At the very least, as the captain of a High Capacity RPT aircraft, I would expect a notice to crew prior to boarding, detailing the seating position of said 'sky marshall' on board and the nature and quantity of any dangerous goods that he/she/it has brought on board. This could be similar to the notification received for PICs. As for the training standard, while I have complete faith in the SAS, I am dubious about these people.