Just got the new "Small Arms Review".  There is a pic of a Knights Armament sound suppressor attatched to a USP Compact.  Threaded bbls are an option on these things?  

The pistol shown was a 9mm.  How would one go about getting one of these in a .45 ACP?

HK was going to come out with the USPC-T in .45 but canned the project, along with 10 round mags for the .45 USPC.  
If you want one you will have to make it yourself and you just missed the group buy (offered here and on HKPRO, snooze you lose) on Jarvis USPC .45 extended, threaded, and o-ringed (HK barrels were not o-ringed) barrels for an unbelievably low price.  Now it will cost you about $240 for the same barrel.   Then with the addition of Heinie Compact Tactical sights and you have the pistol HK was going to make, then didn't.
SAR must have made a mistake because my information is that they never planned on the USPC-T in 9mm, only .45 ACP.

I was aware of the group buy for the USPC tac bb.  Was not willing to give up my poly rifling.  Looks like I'll have to if I ever want a threaded bbl for the Compact.

It probably was a .45 that I saw in the pic.

Some more barrels became available on the group buy.  See this thread and contact the guy about getting one reserved for you if you are still interested.