I'm guessing that in this case GV is set up on sp1 and the sip scanners are still getting through on sp1. Although GV does not use SIP, at default the X_UserAgentPort for sp1 is still set to 5060. I'm guessing that a sip scanner scanning ipaddress:5060 will still get through even if sp1 is set up for GV.
I don't use GV myself, but lots here do. Maybe others can comment if they have been scanned on spX's set up for GV.
If you are using GV, then you could set the X_UserAgentPort to 0 as GV does not use it.