Certainly, Polyurethane over Nylon 6 is possible. Bayer published a technical bulletin about it about 15 years ago. Also, vulcanised PP/EPDM (Santoprene) over PP is definitely done.
I expect some other combinations should be possible, these being:-
Other PP elastomers with PP
PBT block co-polymerssuch as Hytrel and Arnitel over PET or PBT.
PU over other nylons.
Regards
pat