It would sound no different...all tones do is eliminate interference. I don't think there are many PD repeaters without tones, but I know many FDs use CSQ alot.
Tone squelch helps the repeater ignore interference by not being keyed up by it. Tone squelch technically does not eliminate the source(s) of interference. The interference may still be there on the input frequency but the repeater won't respond to it.
I've heard of PD repeaters running CSQ by accident, where the tone squelch function was inadvertently turned OFF. It usually gets turned back on after the repeater is heard rebroadcasting distant co-channel traffic taking place on the repeater's input frequency.
I don't know of any that intentionally run CSQ. I think it in the FCC rules and regs (Part 90) that public safety systems are supposed to use some kind of selective calling system, such as tone squelch (CTCSS) or it's digital equivalent (DCS).