Not even FTA channels?
Those should be working if BDA drivers are ok (and dont require any special tricks).
Any ideas as to why the tuners aren't even detected?
No clue, haven't been working at that area of code ever.
If we added support for the PBDA could tuners like this be [even partially] supported?
PBDA will help with the protected content, but it would require TsReader, TsWriter, EVR presenter... all the content / streamign handling to be done in closed source (and with protected process / video & audio paths). I cannot see that to happen PBDA could be still used if it would provide some real benefits for the FTA content (but it would be still quite big task to take it in use).