Even if this were a translator, where it could RECEIVE interference, it still has to protect the border to 34 dBu F(50,10) or below on Mexican soil. Theoretically, you could overlap over water. But with all the interference from XETRA-FM, it wouldn't be much of a translator even. Like you say, gr8oldies, there were some such applications near the Canadian Border near Detroit. If you look in the International Agreements, you can use concentric U/D interference ratio "circles" to determine actual areas where there is actual U/D interference, but those have only become "popular" recently for FIRST ADJACENT applications near the Canadian Border, don't know about Mexico. There are so many vacant, even some Class C, allotments in SSM, ON that this is being used quite a bit lately. Most of the Windsor and Sarnia Vacant Channels have been used, but many new stations in Canada are on SECOND ADJACENTS, and it is possible to keep the 34 dBu F(50,10) contour within the borders with Directional Antennas, and they RECEIVE and ACCEPT some 94 dBu F(50,10) interference from US Stations. But you have to have that interference situation addressed in the APP.