Arnold for Maya support is there but only for OSX and Linux at the moment. There is a bug in Arnold on Windows which causes it to crash when rendering Ornatrix hair. Solid Angle promised a fix in a month or so, it could be worth emailing them to ask the status of it.
I asked SolidAngle about it. Here is their response
"I'm sorry, but I can't discuss the details of the beta programs of other companies products, but Solid Angle works hard to support third-party developers."
Which make sense to me. Again, woudl be great to see it happen
