My Sony 9000 Edit controller (and the current 9100) was capable of assigning multiple record decks which would then roll and record in sync. The same could be done with 5 playbacks at one time if they were selected to roll with the edit. This is how we did digital video effects in the old linear days. Non-linear systems don't need to do this so they usually only control one deck at a time. If you could get your project to a linear edit suite you could do it easily. Grass Valley 151 and 251 editors and Ampex ACE editors did this as well. Oh, and so did CMX editors. HTH
fire*, smoke*, photoshopCS3
Charlotte Public Television
Well, it's kind of old school but...
If they are broadcast decks with RS-422 ports, you could synchronize them all easily using an "old fashioned" edit controller. Most of these could sync up multiple machines and play them back all at once. And, with time code, it would be repeatable. You could most likely pick up a used one for pennies on the dollar these days.
Just a thought...