I booked a trip through LH, but some segments are on Air Canada. The LH website can't assign seats for the AC segments, but the LH booking reference doesn't work on AC.

I know when I book codeshares on United, they give me the relevant PNRs for other airlines. Does Lufthansa offer something similar?

I'm using my UA frequent flyer #, so I don't think that's an option for finding my reservation on AC.