If I go to a trunking site that I know I am not receiving the site name still shows up on the screen.
Here in Louisville KY I can receive about 3 of the 140 sites on the Indiana P25 system. While the scanner "scans" all 140 of these sites the name of each site is displayed during the scanning process. The scanner "lingers" on those sites my scanner receives the control channel. In that case I see signal indicator bars. That tells me I'm "hearing" the site, but if no audio is coming over the speaker, I'm presuming that no one is transmitting.
This is just like when the scanner is going through systems. It shows the name of the system being scanned, just so you know what it is attempting to listen to.
I cannot open the squelch on the trunking system to hear if the data signal is in range.
I'm pretty sure that's typical for a trunked radio system - you won't hear squelch when you are receiving the control channel of a trunked radio system.
You could, if you wanted to go to the time and effort, program the given system as a conventional system and input each site and the control channels. Then when the radio is scanning, it would stop on those sites that are in range and you would hear the sound of the control channel.
But for the purposes of knowing which sites are within range of your scanner, it's a case of watching the scanner for signal indicator bars and noting the site name.