Platinum Upgrading Domestic Itinerary With Miles?

I was looking on Expertflyer, and I see that domestic upgrades with miles uses the same inventory as SWUs (RP.)

If I look at the upgrade award page on delta.com: http://bit.ly/13YrkCx

I see that an upgrades from unspecified fares classes are 12,500 miles.

So the questions:

• Can a Platinum (or Gold or Silver I suppose) get a higher priority for an upgrade using miles rather than using the complimentary upgrade?
• If the priority is higher, is it like an SWU (which trumps practically everything exept other SWUs) or is it something else?
• On what fare classes can it be used?
• Can it be used on transcon BE??