June 25, 2012
10:40 a.m.
In my observations, the contents of the SIP options response has no bearing. In fact, an error response (such as "not supported") is sufficient to keep the sip binding up, if I recall correctly.
You will also have the joy of making sure your providers support SIP options. Depending on the provider I get any one of these back: 501, 403, 484, 404, 405, 408, 502. Some just plain don't respond, but the big guys do usually respond.