Here's what I have heard, from reliable sources inside of NSW and inside SF.
The Hk Mk23's from the SEAL teams where all sent back to Crane. I believe it was a Command decision, yet some SEAL teams or possibly only platoons refused to send their back.
SF Teams, or possibly the USASFCOM requested them and recieved some of them. In all there where only about 2600 pistols and their respective suppressors and LAMs where put into service in 1996.
You'd have to ask someone inside of SF if any of them are actually being taken down range or if merely used to garner more .45 ACP ammunition for other platforms. One SF guy that I know has said that he's seen them on the ranges with SF guys. If that even means anything.
The Hk45 it's self does not have a threaded barrel for a suppressor unless NSW has gone the route to have Hk supply them modified to outfit with a suppressor. At this time I do not believe the Teams have these.
Maybe one of the current SEALs can shed more light on the subject.