For me:
Zync seemed outsourced - at least overseas.
PRG seemed US-based.
BCE seemed US-based.
Everyday I have not had contact with yet. TBD.
Platinum seemed US-based. This I would expect for being one of the top tier offerings.
Calls might also get routed based on what you are requesting. "Simple" issues might go overseas/outsourced. More advanced issues, such as CLI's, might route to a US-based center.
