If you find me documentation on the sirius protocol I'll definitely look at it.. It seems sirius has taken down any sites that had info on their products, so maybe you can try talking to them directly.
If you use Phoco 1.4 REGISTERED with the -nodesign option in RRConfig, it loads it really fast (phone connected or not)... I have found that starting up Phoco 1.4 NON-REGISTERED does NOT work consistently, so you should likely run it on your windows startup minimized or whatever.. I have not and will probably never do any testing with any earlier versions..