It seems unlikely in these cases. In the case of the PR 18 the other bidder leapfrogged over me several times. One minute I'm the high bidder, the next minute I'm outbid. This went on for awhile until I gave up. Then it shows up on a their website at a fixed price.
To reiterate, though, if Metro was bidding on a book put up for sale by a third party, and was acting just like any other bidder, subject to the same rules and processes as any other bidder, and Metro's purpose was to buy the book for resale, then there's nothing nefarious here. It only would be a problem if Metro's purpose in bidding was to drive up the price paid by someone else.
Frankly, I'm not concerned by Metro outbidding folks on a third party's books, but I would be concerned if Metro often turned up as an underbidder on a third party's books. And if Metro is bidding on its own book in the fashion you describe, then I'd be shocked.