I am currently researching the new Digium phones and how they would receive provisioning. I am reading up on their DPMA module and how it works. this method looks slick, but there could be a chance that this only works in STE, and then only when the phones reside on the same network. It appears it registers itself as an Avahi/mDNS service for discovery.
I have already found one glitch in an example config and am waiting on a callback from one of their software engineers. Apparently digium doesnt know how to read the RFC for Alert-Info headers any better than trixbox does. The value of the Alert-Info is supposed to be nested inside of left-angle and right-angle quotes < > . For example, out of the box, polycom uses the value Ring Answer for their ring-then-answer setting. Therefore the dialplan would appear as
SipAddHeader(Alert-Info: < Ring Answer >)
the problem is that trixbox and other programmers always did it without the brackets, and phones generally accepted this. However, routers that depend on libosip2 will drop these packets. that means routers such as siproxd, or opensips, or SER or these others, when in use, will simply not pass the request to the phone since it violated the RFC. I discovered this problem about 3 yrs ago when I started experimenting with siproxd.