Possible? Sure. Just like it's possible that I could win the national lottery.
In practice, multiple companies bid for contracts, and all of the bids have to be of the form "Deliver $X in $Y months for $Z dollars".
No company is going to accept "Choose us, and we'll work until you're happy with the product or you run out of money, whichever comes first".
Agile doesn't work where there's competition for the project. It can't, because the buyer of that project cannot evaluate "we'll work until your money runs out" against the other bids that state "$X in $Y months for $Z dollars".
Agile works well for internal teams that are sheltered from having to provide competitive bids.
Which still loses to the other bidders who say "$X in $Y months for $Z dollars".
Typically, the intermediate step is to tie some compensation (such as a bonus) to a particular metric, but why not just go whole hog?
“We’ll work collaboratively and evolve the product over time in yet-to-be-determined ways” can work when you have an established relationship and 2-way trust, but there’s not much of that during an RFP. If a competitor commits to their biggest asks, and we don’t, we lose the RFP.
That's just pushing the issue one level higher. Most likely both the customer and you would be happier if you were able to iterate with them rather than building the thing they thought they would want however many months back. (And while it may be harder to set up that kind of contract, it's absolutely possible)