It actually depends on the country (and I assume even state and city). Where I grew up, most firemen actually sleep at home and not at the station. They have "normal" work hours during which they do non-emergency work, such as train, maintain equipment, raise awareness for fire prevention, etc. and they get paid for a target work week of ~40 hours. Being called out "outside" of hours is compensated, AFAIK in TOIL. Point being, there is no one size fits all model and it has to work for your environment.
Asking for being on-call for 7 days to be equivalent of 168h of work, i.e. after you have been on-call for a week you go on vacation for 3 weeks is just as unreasonable in most situations as companies asking their staff to be on-call without additional compensation.
Asking for being on-call for 7 days to be equivalent of 168h of work, i.e. after you have been on-call for a week you go on vacation for 3 weeks is just as unreasonable in most situations as companies asking their staff to be on-call without additional compensation.