Yep, drug and alcohol testing, still somewhat novel in the UK, has been the norm in the US for years now. Under our system, the alcohol limits for mechanics, flight attendants and dispatchers are the same as for pilots (.02% removal from duty, .04% loss of license and major legal woes).
Also, under our system, if you apply for rehab, it does seem to give you some legal protection.
In the recent America West incident in MIA, the pilots jumped bail to go to rehab right away. It annoyed the judge but they were later able to cop a walk on some of the more serious criminal charges (see:
http://www.sun-sentinel.com/news/loc...home-headlines ).