I was wondering if this could be a problem with submissive urination? Our last dog, a very high strung terrier mix (but the most lovely dog) had this problem when she first came to live with us. We read as much as we could on the subject and followed all of the suggestions. After a few months she pretty much was rid of the problem...though when she was really scared of someone or intimidated, she'd still pee...but that became more and more rare the older she got.
Here's a link for you:
http://www.hssv.org/LIBRARY/PDF/Behavior/piddles.pdf
I think you have to have adobe acrobat. If not, look up submissive urination on the web...you'll find lots of info.
I wish you all the best. It's a difficult situation and I wish I had the answer for you.