I just did this a month back. I had to create like 15-20 piping systems (to match the services listed on the P&ID's we were working off of).
I had to go to Style Manager, and under Multi-Purpose Objects, then under Layer Key Styles, then MEP Object, I went and made layers that pertained to each system, each being pre-fixed by "M-SY-PIPE-".
Then I went and made a system for each, and assigned them each their own respective layer. I found that if you mistakenly place a pipe on the wrong system, it'll easily change to the proper layer when you toggle it to the correct system. I have found that if you do Match Properties, it does not seem to do this, it'll change the layer, but not the system, and if you have enough piping ran this is extremely difficult to detect after-the-fact.
Worked like a charm, except for the hiccup with Match Properties. Although, I am using 2009, this may not be the case with 2010, I'm not sure until I get there.