Red bellies will munch on the others if they manage to grab one, but doesn't mean you wont have the others still hanging around. There is no territoriality involved here. Tigers are absolutely everywhere regardless of what other snakes are around.
IMO red bellies would not be able to keep up with tiger numbers. I reckon for every red belly you see, there is probably 6 tigers within 1km radius.
Go for a walk along a creek or swampy area one morning 28-30C degrees preffered, usually 10-12pm... and count how many tigers you see vs. red bellies or browns. You'll see what i mean.
We lifted one of them kids sand shell things once in yarrambat and there was a tiger sinking its fangs all over this black. Unfortunately for the tiger , it was half digested and it was all over red rover. We let if finish its business and bagged the red later.
When my mate went to relocate/release it, he found 2 snakes in the bag. One of them had seen better days to say the least.