Hands-On: Samsung Galaxy Indulge for metroPCS

It's publicly known that MetroPCS is trialing VoLTE - a simplified form of IMS. What would be nice to understand about the SCHR900"Craft" and SCHR910 "Indulge" handsets is what sort of voice service they can support over LTE packet switched networks.
VoLTE?
VOLGA?
Over-the-top SIP clients?

Anyone know?

/torrmundi