Actually quarantine should be the same for any species of snakes and yes even if rare OPMV have been found in colubrids as well.
If you are really paranoid like me yes 4 snakes from 4 different sources means 4 different QT locations, think about it this way it only take one animal in proximity of others to start having issues so what is out on those 4 snakes one has issues even something as simple as mites?