Domain Backordering

Sorry, I don't know the answer but your question is very interesting. i am also interested in that matter. I think it's best to ask the register. They should let you know.

I see why you are asking the question but it has to be debunked.
If you are looking after a name in pendingDelete (or redemption which will go in pendingDelete), it's important to know the current registrar, if he is involved in backordering/dropcatching has no priority over the domain.
The dropcatching game is "fair" to all registrars, each registrar is given the same accesses to the registry and they mostly compete with the amount of accreditations they each own.

Now if the name is just expired, before redemption, it might be possible to participate in the auction, if the current registrar has one. If it doesn't have one, it's highly unlikely they will be able to sell you the domain unless their ToS allows them to do so.