I tallied up all the ratings earlier today, sourcing from
http://www.tvtonight.com.au/.
Across 26 rounds, the average ratings in Brisbane was 268.5k (Sydney 380.7). 7:30 game only.
The average of the Broncos 18 games was 287.8k.
The average of the other 8 games was 225k (243k minus the game shown on GEM).
Can't really compare it to Cows because 3/4 of their games were against other Queensland teams, you would need to look over previous years to get a better idea how their ratings hold up against some of the lower drawers. Their non Qld game was Vs Dragons and got 274k (R9).
Titans are similar, but with more 9:30 games also.