BLE could do that too via advertising packets. I don't know if any devices actually do though.
Also the connection process isn't power-prohibitive for BLE, and it doesn't have to take a long time. It's just that most Bluetooth software stacks suck balls. Basically only Apple's is good.
As I recall BLE only supports hosts connecting to 7 peripherals simultaneously which is a bit rubbish, but if you're a gym with some custom ANT+ receiver you can definitely get a custom BLE receiver that can connect to more devices (assuming someone makes such a thing).
Many devices put the data into the Manufacturer-specific part of the advertising packet. It's a workaround. The problem is that it's non-standard so if you're a provider of data management for group fitness you have to have custom code for each manufacturer (and sometimes different devices from the same manufacturer). And it's especially fun when the manufacturer's published data spec doesn't match what the device actually puts out!
I don't know how difficult it would be to connect, grab a bunch of data and disconnect from 24 BLE devices in a one-second period, which is pretty much what you'd need to be an effective workaround for ANT+. In a competitive environment, data from each device changes very rapidly.
Also the connection process isn't power-prohibitive for BLE, and it doesn't have to take a long time. It's just that most Bluetooth software stacks suck balls. Basically only Apple's is good.
As I recall BLE only supports hosts connecting to 7 peripherals simultaneously which is a bit rubbish, but if you're a gym with some custom ANT+ receiver you can definitely get a custom BLE receiver that can connect to more devices (assuming someone makes such a thing).