Treespotter, we use the half body rule in my company as well, however this brings an issue to the table of maintaining a single "uniform" to be worn at work.
If I was not hastled constantly by the higher ups about wearing hi-vis pants, i would by all means wear them. I do not like the fact that the crewmen of my compant must wear Navy Blue/Navy Blue or Navy Blue/Gray. They think it give a more "professional" appearance to the customer if we are all in the same colors as opposed to showing up with some guys in jeans and a cut off Metallica t-shirt.
I would love to wear something hi-vis on my legs, since the neon green pull away mesh vest can get rather agrivating while clearing brush. BUT... as I said, unless I can get the uniform (which was only established in december) to take exceptions for safety, I am on a street with no sweet pants.