Inqwe,
At one time in the Sanderson, Texas area on the Rio Grande River a number of Mexican fighting bulls crossed and got on private US property...Most ranchers roped them and hauled them to the sale in San Angelo, but a few interprising gents sold them to clients from other parts of Texas, to folks who would shoot anything...

The truth is it was a sham, a canned hunt of sorts..Most of that was stopped when the border was closed for hoof and mouth..then the river riders shot them and burned them on the spot....

It pops up every once in a while, when a sucker can be found, and the rancher is willing..Cattle get wild in that big country, but as soon as they are put on feed they domesticate almost over night.

There are many wild cattle in Mexico and most of them end up as roping steers in the USA at a premium price, then go on feed when they get to large and end up on you plate....

I am sure that anyone could find a rancher that would sell you a wild cattle hunt for the right amount of bucks, and that would be anything over market value plus room and board....Kinda like Barbedo sheep, and spanish goats and some of the other stuff they sell as game...