This is what I have gotten from coworkers. They are both firing on the same order confirmation page.
Site Catalyst: Uses the Page Data Layer to capture orders
Test and Target: Uses an Mbox on the page to capture orders
I am not sure what the difference in those are or if that could be the reason why there is a dependency.
Site catalyst is showing about 190 orders whereas test and target is showing about 30 orders for the same time frame.
Sorry I don't have more info, but I am new to both tools so just trying to get a handle on things.