Sigtran or MTP interconnect?

An issue has arisen in relation to the emerging communications
conference (www.eCommMedia.com); the short of it is - are people still
doing MTP interconnects? If so why? To be more specific, are people
still building boxes then going to incumbents around the world,
running thru tests (Q.78x) to get them certified at high cost etc. in
each country? Or do all incumbents in developed nations now accept
Sigtran for signlling interconnect? Any experiences would be welcome.
I know in the States that Verisign has supported Sigtran interconnects
for around 5 years, but I wonder what the case is, specifically in
Belgium?

Leaving aside the incumbent issue (i.e. do they accept SigTran
interconnects on the whole) - does anyone see an advantage of using
MTP?

Thanks in advance.

Lee