Does Xfinity offer SIP trunk service natively for residential customers (e.g., no voice modem)?

I have a Gigaset C530 IP Hybrid VoIP/Fixed line phone.  The fixed (analog) line service does work, but not all features are recognized (example:  If I have a new voicemail waiting, the visual network mailbox indicator on the C530 IP does not indicate as such).  Unfortunately, Gigaset does not manufacture any other phone product for use in the United States, otherwise I would have bought a landline-only/analog system.  It's a real shame too, because the build quality on their products is great (seriously, their consumer products have no equal).

Admittedly, I'm not holding out much hope that SIP trunk service is available natively for residential installs, but it would be nice to leverage all of the features the Gigaset C530 IP has to offer.  I get it that the voice modem is what makes it easy for customers to connect a phone, but for geeks like me, is there a chance that the voice modem could be taken "out of the equation" and I could connect directly to Xfinity's SIP trunk service via ethernet?

Thank you.