Try emailing sr-users list you will likely get better responses there.  Also for what I can make of your question, if your asking if you can do a voice/video call to any endpoint from any carrier, the answer is likely no, it will be dependent on the path in between that it takes and whether or not the requested communication methods (codecs etc) are supported.  If you are asking if you can complete this through kamailio, kamailio is simply a proxy so if the scenario is:

a < - > kamailio < - > b