The brain trust at Cumulus doesn't seem to know what to do with its AM Talk stations. Not one in a large market is doing well. WJR Detroit and WMAL Washington, which are usually top ten stations, have seen their ratings drop recently. WABC NYC, KABC Los Angeles, WLS Chicago, KGO San Francisco, WBAP Dallas, they're all at or below #20 in their markets. (Same for WYAY Atlanta, although that one is on FM.) You can't blame poor signals for these ratings tumbles, except for KABC.
So maybe Cumulus thinks adding sports play-by-play to WLS might help it regain some lost glory, when it would regularly be in the top 10, before People Meters came along. Chicago has no FM Sports station. CBS (WSCR 670) and ESPN (WMVP 1000) are both on AM. So maybe Cumulus thinks it can be a bigger player with some live Sports action on 890.
That probably wouldn't be possible for WABC since NYC has two FM Sports stations. I'm not sure why iHeart jumped on The Mets for 710 WOR, other than iHeart leader Bob Pittman is said to be an investor in the team. So far, Mets broadcasts haven't meant much of an increase in WOR's summer ratings, maybe a few tenths of a rating.