One of those terms whose casual use in writing gives lawyers fits.
Under Canadian law, partnerships are not separate legal entities; they occur when two or more companies operate in business together and share the profits (they hope) and the losses (they hope not) in proportion to their ownership share. Partnerships also involve joint-and-several liability, which makes one partner responsible for the bad stuff any other partner does (paraphrasing the legislation).
In proposal-speak, by contrast, “partnership” is a squishy term, mostly meaning that the bidder intends to work nicely with someone else: another company, perhaps, or the client. I have never seen a non-joint-venture partnership as the bidder for what I’m sure are reasons to do with liability; conversely, I’m not sure I’ve ever seen a proposal that didn’t talk somewhere about “partnership.”