According to this, last year Nine’s main channel got a considerably higher percentage of the audience between 6pm and midnight in Sydney & Brisbane than they did in Melbourne where they were barely ahead of Seven.
Now admittedly I’m not sure how they’re doing this year (although I’d guess the gap is considerably closer due to things like GC2018, the decline in Ninja Warrior, etc.) but I stand by my point. Nine definitely should do what they can to improve the Melbourne ratings of Today, but not at the expense of Sydney & Brisbane.
Aside from differences in things like the football, just about every program on every network gets higher numbers in Melbourne than Sydney from what I’ve seen.