Hi Max,
Yes. It is possible to use EF6 views in EF5 apps after some modifications. I just tried - here is what you would have to do:
Change namespace for EntityViewGenerationAttribute from:
System.Data.Entity.Core.Mapping toSystem.Data.Mapping
Replace the EF6 HashOverMappingClosure with the value from the EF5 pregenerated views.
The two above steps were enough to make EF6 views work on a EF5 app - it was very simple in my case - just one entity but I think it should work in general case as well.
Thanks,
Pawel