When the NHL wanted to take over all the team websites, the Rangers fought it tooth and nail. Eventually, the Rangers lost the battle. MLB could try to do the same, but the fight would be MUCH bigger and more expensive for YES and NESN. SNY? Cohen may support the league as he doesn't own it, Wilpons still do. Before the team was sold, contract was written so SNY paid very little to the Mets for the rights.
Here's the thing though. For what MLB is trying to accomplish, they don't actually really need to get all 30 teams at once, and the "fight" is going to be a tiny bit of talk in dribs and drabs and not like "Everything coming to a head."
They just need a tipping point where they can pass a grandfather rule that either (a) separates streaming rights from local broadcast rights at the end of their current contracts, or (b) drops the exclusivity from streaming rights.
They have six now (COL, SD, ARZ, CLE, MIN, MIL). They also don't NEED Toronto ever; it just doesn't apply to them. They can definitely get the Athletics as part of the terms of relocation when they leave California.
Eight more teams were just dropped by Bally's and four of them would easily vote for it, because the collective distribution would be higher than what they can generate in their small markets (CIN, KC, MIA, TB).
BAL/WAS, where they co-own MASN together but arguing/disputing the revenue split constantly and that's up for renegotation in 2028. Washington feels they're getting hosed, and Baltimore will be "small market" when that deal evens out.
Basically somewhere between 2028-2031, like after they award expansion teams and those guys get to vote, they can probably pull off a "No future TV contracts include local streaming rights" rule.