The estimator is willing to make an educated guess and assume the risk of a failed installation by adhering over the old flooring. I have done that many times with no failures, however I would not attempt that kind of installation over tiles on a slab in direct contact with the earth (i.e. on grade or below grade). Yours is suspended concrete construction, so I doubt that you'd have any problems. The 'other' estimator's assessment is it "could cause the tiles to pop up."

When you tap on the floor in many places, is it a solid sound, or do you hear many hollow sounds?

There are underlayments that would help make for a quiet floating floor. I am just of the opinion that walking on them is somewhat creepy.

Estimator 2 is correct...The tiles could pop..but doubtful...Why not a floating real wood if you want real..they make many of them..Call your local flooring stores and ask if they have any locking real woods that are approved for floating. You should find many as NRF distibutors carries several that can float and they service stores in New York City. Or of course laminates will work also...

galleycook,
Engineered floating wood floors is what you are looking for. This way you can have you wood floor and not have to worry about tiles pop. Below is an article about choosing your floating wood floors in our Blog. Hope this will help.
"Choosing Quality Floating Wood Floors
For your condo, basement, radiant heat floors
You are just a few clicks away from a new Wood Floor for your home! We are talking about clicking together your brand new floating wood flooring.
Floating wood floors are now installed on any hard surface with simple a click lock or tongue & groove system. All floating floors are bound to each other and not to the sub floor. This makes it possible to expand as one piece rather than individual boards. It's ideal for areas with higher humidity such as basements. Since floating wood floors will expand and contract as one unit, the chances of cupping or gapping between boards is greatly reduced, but be sure to leave space along the walls and cover them up with your baseboard as this allows for expansion.
Unlike its counterpart, click lock floating wood floors are much easier to repair if a specific area is damaged. A great example is a dish washer flood. You would simply unclick the flooring up to the damaged area, then replace the damaged boards and reassemble.
Another benefit is installing it directly over ceramic, tile, or any hard surface. Tearing out and disposing your old flooring is quite an extensive project in itself, but that's no longer necessary.
Floating engineered wood floors have become more and more popular amongst home owners due to the simplicity of installation and stability in structure. Besides a few species, they also worked well with radiant heat systems and concrete basement sub floors. Floating engineered flooring is typically installed above the underlayment, a foam or cork material, which acts as a barrier to moisture and sound.
European styled floating wood floors often have a 3-ply design with the top wear layer being hardwood, lumber middle core and balanced base veneer. When the floor has a 3 to 4 mm (1/8" to 3/16") wear layer, it is considered high quality for several reasons. First of all, the thick wear layer can be re-sanded and varnished a few times giving it the fresh new look as when you first installed it. Secondly, floating wood floors with a thick top layer prevents you from feeling the "bounce effect" while walking on it because it tends to sit on the sub floor firmly due to the weight of the hardwood.
While most engineered floating wood floors are designed with a click & lock system, some can still be tongue & groove which requires edge glue. There are advantages to each design. Builders and Diyers enjoy the floating wood floors with click & lock system more due to the benefits of easy installation. Meanwhile, contractors could favor the tongue & groove floating wood floors more because they can be installed by nail-down and glue-down.
Now you may be asking yourself. Why should I choose floating wood floors over laminate flooring which is just as easy to install and has the similar wood grains? Well floating wood flooring is real wood that offers all the advantages of real wood floors. The biggest advantage is that real hardwood is warmer on your feet. Like solid wood flooring, floating wood floors with thicker wear layer can also be refinished a few times. Remember the thicker the wear layer the more times you can refinish. Quality floating wood floors should last 40 to 50 years!
Recap:
� Not all the floating engineered wood floors are made equal. Total thickness and wear layer (top hardwood part) make a huge difference on the performance and life span of your installed floor.
� All wood products will have some expansions and contractions during season change.
� 1/8" or thicker wear layer and 1/2" and thicker total make wood floors with optimal floating weight.
� European styled 3 ply floating wood floors provide good stability.
� Make sure your sub-floor is leveled within 3/16" for every 10 sqft before installation. The most common cause of hollow sounds and noises are from low spots on your sub-floor.
� A good 1/8" acoustical underlayment, such as Acousti-Cork or Floor Muffler, will improve your floating wood floor's performance and improve sound barrier quality.
� The bigger area you are covering, the thicker floating floors it requires."