Yes, it is common. If you put it on a uncommon frequency, who will hear it? If it's on a common frequency or thru the repeater, people will say "hey why is it beeping, lets call the radio room...." and then they can figure out what it means.
SCADA is a VERY broad term, it's not a specific technology or codec. This is probably monitoring at a remote site, or a trouble alarm, or a status alarm for a repeater ...etc.