If you’re going the SCCP route, I have no idea. Never used SCCP on Asterisk and I honestly don’t recommend it.
SIP works just fine in most cases, especially with the Cisco patch that is available here: http://usecallmanager.nz/patching-asterisk.html
I have BLF working just fine on my phone with this patch.
SIP is what I recommend and will probably save you some time and headaches.