I looked up Easyboard - never heard Hardibacker called that. Yes, I use it for certain mosaics. In fact, I'm using it now in a project as the floor and courtyard for a little church I'm making for a friend. Lowes carrys a tool for scoring it, but I found the tool to be no easier to use than a box knife. You score and score and score and score some more until you can bend it off. Not the easiest thing to cut but it can be done. I used it to make a giant flower, a butterfly (which in the picture is upside down - gotta change that) and a heart shape when I was making the last extension to my Fountain Surround, for which I'll provide a link. I made those three things to cover the rebar stake ends my yard man left exposed when he was putting them into the ground. Be sure and wear a mask - it's concrete and gives off dangerous particles. Lowes won't even cut it for you.

Oh - I left out the giant tear drop shapes mosaiced in mirror that you see in the photo - they cover a rebar stake too. Also I used Hardibacker to make the trim around the top of my patio - sorta my tent theme that goes with the "circus in my mind", as one former member of this forum said of me - if you look further in my album. It's a wonderful material to use for exterior mosaics.

Thanks slow! I don't *think* it IS exactly the same as Hardibacker. I found this link http://www.reedconstructiondata.com/documents/FS/specdata/092800_10000327_01_SD_22332.pdf but that didn't really clear it up for me! It's the "little brother" of a cement backboard and supposed to be very easy to use. I bought it from my favorite stained glass store and the owner said it was perfect for my purpose (bathroom wall). The spec sheet says indoor-use only.
I'm about to attack it with a box cutter. I'll let you know if I win the battle!

I read the description - the part about exterior use seemed to be re the wind, so that wouldn't affect your butterfly. It appears to be good enough to last outside. Good luck, and please give us pictures of your WIP.