I also enquired with a local and he was of the opinion they are VERY low on numbers, hence the regular off lines.
It happens, hope they can get though it.
By the way Mallee Fire,there is no dual response for RCR in whyalla, the only reason they ever go is for lighting or if the MFS are already busy, but Pt Augusta go for COQ if they are busy so thats rare. Often when they are responded off the bat is a mistake.
If SES in Murray Bridge is offline Murray Bridge MFS is default rescue for all of the SES area.