Could you use something similar to detect digital / data radio transmissions?

Motivation: here in Linz we have electronic signs at bus and tram stops that display how many minutes until the next bus/tram arrives. I believe those signs somehow get their data via radio (they have antennas). I know nothing about the technology used, but since they were installed more than 15 years ago they probably don't use the cellular network.

The company also offers an API with live data, but for some reason the estimates from the API are not as precise as those on the signs. So I'd love to somehow intercept the data sent to the signs.

Does anybody have an idea how to go about that? I know nothing about how radio works.