Morning folks, thanks in advance.

Trying to get my aunt, who'd need accessibility assistance, from ncl-yyc.

There's a specific WestJet flight from LHR to yyc that is attractive price wise, but clearly that means getting to LHR is the issue.

There's no option on the BA site to book BA-Westjet so I've been saying it's not possible to have that itinerary on the same ticket, which it would have to be to get assistance through Heathrow.
Am I right?

My sister (that's who's in Calgary), keeps sending AI search results saying BA and WestJet are partners and it would be possible.