A dog can be trained to indicate when it detects both explosives and drugs, but as mentioned earlier, TSA does not train its dogs to do both, no reputable trainer will do so, and no law enforcement agency, certainly not one in the transportation sector, will employ a canine trained in both. Dogs do make mistakes and could give an incorrect indication for what it has detected; the consequences for such a mistake could be catastrophic and no governmental unit will take that risk.

There are thousands of law enforcement agencies just in the US so it is not possible to definitively state that none but TSA and its partner agencies are using PSCs. But I have not heard of any US federal entity other than TSA having a PSC program nor have I heard of any airports or mass transit LEA having their own canine teams not supplied by TSA using PSCs.

There is a move afoot on Capitol Hill to augment the number of canines in service for the transportation sector by using what are termed "private sector canines." These are dogs that are sourced and trained by third part contractors. TSA is opposed to this for consistency and quality control purposes; TSA's program is robust and highly respected but it feels it would not have effective oversight over the quality of the dogs and their training if conducted by contractors, even if some/many of them are highly reputable.