Emergency warning equipment doesn't need to be active to drive under exemptions.
Yup one of the myths that people seem to be under is that the police etc need to have their lights/sirens on to use their exemptions, iirc in law there are basically no limits, but they have to follow their force/service rules*.
From memory the emergency services get a lot of stick for using their sirens, so usually try to not use them too much and might even turn off the lights if the police are trying to get somewhere quietly in an emergency.
Re the red light, i've seen comments by emergency service people (including the police) saying you don't have any exemption for crossing it to let say an ambulance through, but that if you do get a fine and can show you did so safely the magistrates/people giving the fines can waive it, however that was a few years back.
*The reason most forces have rules in place so that officers need to get permission/inform the control room if they're going to speed (above a certain level?), and why a few years back a police officer doing very high speeds was found not guilty when he claimed he was "training" in his police car whilst on duty, apparently his force didn't have that specific rule in place so he wasn't breaking the law in terms of speeding because as an on duty officer he was exempt, and his employing force hadn't put it in the regs that he needed permission to do it.