Serge: yes and no---it supports onnet SMS over SIP, but not offnet (at least not without modifications.)

Serge: it actually might work inbound possibly (I haven't tested) but it wouldn't work outbound.

Serge: no, I just checked the Kamailio config and it appears it wouldn't work for inbound either, unless you modified the Kamailio config to accept messages from external sources, and route them properly.