Not quite true - most of the Retained stations have vacancies, even in major population centres that support more than one station. Leeton is a rarity, the next closest stations are both short.
I think that the cross over thing is more to do with having other things to do, rather than any interservice stuff. Sport & drinking is very big here
And despite the the drought problems people have plenty to do (i.e. there is plenty of work). Yanco which is the closest RFS brigade has the feedlot/meat works & a big farming community plus state forests, so its in their best interest to have a strong brigade. Again they are 7 - 8 kms from the Rescue Squad so to be in both would potentially leave their community unprotected.
I think over the years the shire has worked things out very well for themselves, and everyone is happy to do their own thing. Plus thereis heaps of community spirit!
Finally out of interest the controller of the local SES is also the boss of the local rescue squad & yet they are totally seperate entities - on paper anyway
cheers