I have a friend who has the patch and yes they can be contaminated very easily.
I am curious as to weather or not the sweat patch can be contaminated by your pardner? For example, if your pardner drinks and sweats during the night and gets up against you, will this cause a positive reading?
While I have never heard of a person testing positive for a sweat patch that came into contact with someone else (not ruling out the possibilities here), it's best to stay away from people who would be using anything that would cause you to test positive for something or even be acussed of doing wrong. As a previous probation officer, I must say that the officers who monitor that stuff want to see that person stay clear of all situations that could cause their clients to get into trouble. Stay positive and hopefully the person you're mentioning here will have an open line of communication with their probation officer. A clear line of communication can overcome most probation violations if handled right. Good luck!