I think your view of marijuana is a bit skewed, veneficus. Getting that many results, doesn't solely prove your point.
It may impact neuro function on schizophrenics, but according to this (unless I'm misinterpreting it [which is possible, I'm tired]) it is only a temporary worsening of the disease, not cannabis being the cause of the disease (which is what I interpreted your response as somewhat being)
http://www.cannabis-med.org/studies/ww_en_db_study_show.php?s_id=213&&search_pattern=ANXIOLYTIC
I can PM you to the site that I found the article on, if you wish.
Now, on the actual topic that the OP was talking about.
Personally, I see no alternative to UA's. As far as the law is concerned, THC is illegal and they obviously test for THC. As long as you test positive, its a DUI. You are still under the effects of the drug, because it's still in your system (not saying this is right, but from the legal aspect).
As many others have said, though, the public service world is not fond of illegal drug use, so, I see no place for it to be in their system in the first place.
Edit: I'm genuinely surprised at how many people seem to have such a view of degradation on cannabis users on here. I haven't encountered that so far in person in the EMS world (although my experiences are limited). I don't smoke, but I definitely don't look down on people that do. Personal choice, IMO.