I hope they make the mistake of testing a crew that shift following short change, that'll be interesting to say the least.
I'm ok to pass the tests myself, but I still don't agree with the policy especially when, as someone else mentioned, the pee test encourages casual drug users to switch to hard drugs.
Personally I'd be more comfortable working with a guy who smoked a few joints 2 weeks ago than the guy who snorted a few lines two days ago.