I think MP's current drum tech Jose was also his drum tech before Eric Disrude. I don't know if Eric stayed on because he got more money or if Mike just decided to bring Jose back anyway but you're right, it is interesting.
If memory serves me correctly, MP had Eric as his tech beginning in 2004, and this was because Jose was unavailable (or wasn't teching at that time). As you mentioned, techs do work with other bands, which is what Eric did, and was unavailable when MP needed him in 2009. By this time Jose was available and so got his old gig back again, and has since been MP's tech for most, if not all, of his gigs.
As for how Eric started teching for MM, I haven't a clue, but it could've just been a matter of calling him up since the band no doubt had his number and was already familiar with his abilities/attitude in teching for MP.
Side note: talk about 2 completely different personalities - Jose is a world class jerk to the fans, where as Eric has always been very cool. When I found out that MP had Jose out with him again, I was bummed.