Hi.
This is the code I use whenever I want to insert a timer (in the example 5 seconds) between the activation of the internet connection (in this case ANY, but applies also to wifi, etc..) and the register to the sip server. The third command

Code:

dbus-send --system --type=method_call --dest=com.nokia.icd /com/nokia/icd com.nokia.icd.connect string:"[ANY]" uint32:0
sleep 5
mc-tool request sofiasip/sip/_313_40172_2e26_2e0_2e20 online

In the third command, you can get the address/ID/whatever of your SIP account executing the command:
Regarding the issue about register attempts from online-->offline: I also have it .
Whenever I switch from WiFi (online) to 3G (offline) I can still see a few attempts to register....
I hope I didn't mess this up
Regards.