It has been a problem at many companies, including the aircraft manufacturers that I have worked for. A friend that works at GM Arlington has told me worse stories about alcohol/drug problems out there. And it was only two years ago that Ford workers were caught taking 4 hour long drinking lunches on company pay:
http://forums.anandtech.com/showthread.php?t=249190
That forum post has a video link that is dead, but gives the overall idea of the incident in 2008. The companies have to try there best to prevent such violations of policy, and the unions need to cooperate with the company when violators are caught... we will have to see what the UAW does.
XS