Here are some links on submissive urination:

http://www.dogdaysusa.com/behaviorcenter_urination.asp

http://www.canismajor.com/dog/ttouch3.html

http://www.veterinarypartner.com/Con...151&A=1119&S=0

Hope they help. I've had a few foster dogs with this problem. One was a young adult male Pit mix that would roll over on his back for a belly rub and then *squirt squirt* all over himself and anyone that got too close LOL. The other was a female Heeler. When I called to her she would run up, squat and piddle (seems to be a Heeler trait).