These Mexis can't do interstate hauling. International only. This would put serious limitations on their profitability because the further away from the border they get, the harder it would be to find a backhaul and without a backhaul, there is no profit.
To solve this problem, the Mexis had to develop relationships with US trucking firms. In other words, US trucking companies have bought into Mexican trucking companies. Usually at the 50% level. Although I don't know any specifics, it is likely that some Mexican trucking companies have bought into US companies.
And this is part of the rub. These US companies that made the investment in contemplation of phase-in of NAFTA trucking regs were denied the chance to make a profit on that investment. But the Teamsters benefitted.
This whole thing is just another pile of dog doo that Clinton left behind for Bush to clean-up.