Interesting. I wonder what is keeping them from cleaning up like normal glass. Is there any sort of coating on them? Clearly thy will have more oil (i.e. from peoples hair, heads, and hands) on them where Dawn dish soap will probably be more indicated as a cleaner here. Have you looked at any of the wax and oil removers that folks use before painting?

I've tried kitchen oil cleaner once and while it removed the stain I was trying to remove it made new stains from the microfibremicrofiber I used.. They do have an anti-fog coating but the other busses do as well and I didnt have as much of a problem with them. It seems this exact model is like that.

I've used this homemade glass cleaner that contains Dawn. My husband used to use a hair gel spray that ended up all over the bathroom mirrors. It cleaned it right up. Use old wadded up newspapers to clean instead of towels.
This:

• 1/4 c. rubbing alcohol
• 1/4 c. white vinegar
• 1 Tbsp cornstarch
• 2 c. warm water
• 2-3 drops of Dawn

I like a product "Invisible Glass" . It's much better than Windex. It really takes the film off the insides of windshields. Used by auto detailers.

Use a microfiber cleaning cloth.

Invisible Glass