In the early 80’s, some regional South Australian commercial stations including 5SE Mt Gambier would relay 5AD Adelaide after hours and overnight. Unlike these days, the relay was a complete relay including Adelaide advertising, mentions of 5AD and everything.
The reason I’m bringing this up now is that there is a discussion in another thread of a similar thing happening right now in some markets in regional NSW and SA, only it’s TV rather than radio and it’s not just after hours, but all the time, on one of the three commercial stations in some smaller regional markets where all three commercial stations are owned by the same owner. In those markets, one of the channels is either completely or mostly a relay of the state capital’s channel.