WTVX's only news use was for hurricane purposes and was always an albatross; frankly for as little as we hear about it, WBFS could sign off without any advanced notice at this point and very few people would even remember WBFS existed. As much as political revenue is something to be chased, it's probably an incredibly low amount on your average MyNetworkTV affiliate, and a little more, but still negligible on a CW affiliate since you have your usual mix of low-wattage advertisers giving loyal year-round revenue on court show/sitcom blocks enjoyed in offices, restaurants and medical facilities marketwide.
The Dallas duopoly is likely very used to doing multiple newscasts for both KTVT/KTXA and have it down to an art, along with WCBS/WLNY; WBBM hasn't done anything outside of traditional timeslots outside of 'at your desk' shows and social. Station strength plays into it easily, but having the ethic/ability to produce multiple newscasts is likely much more of a factor.