There's been a disconnect for a long long time. The ACTRU was formed to breakaway from the NSWRU as previously the ACT fell under NSW Country. NSW and Qld always thumbed their noses at the ACT sides when they played each other. It got worse when the ACT gave NSW a proper hiding 44-23 in the mid 90s.
The ACT's 75 year anniversary video gives you a good idea of how much animosity there is between the ACT and NSW when it comes to Rugby
https://www.youtube.com/watch?v=p6e-SejwHNc Geoff Didier says it best 'it appears that there isn't much hatred anymore from the Brumbies players towards the Waratahs, like most old boys I hope that isn't the case as we still hate them.'
This is before we discuss the hatred between NSW and Qld then the internal rivalry within NSW between the Sydney Rugby Union who had their own rep side, NSWCRU and the Suburban Rugby Union.