Been reading a few of the older threads re blues and twos on private ambulances, whether they need to be removed if on non emergency work etc etc, and thought i'd share my experience / interpretation. My company operates event medical & rescue cover as well as critical tissue transport. We have a liveried Freelander fitted with blues and siren, which as it has no stretcher facility we've had to tax as a PLG after many many discussions with those lovely people at DVLA. We also operate a rapid response motorbike, again liveried and fitted with blues and siren. This again has had to be taxed as a motorcycle due to the stretcher requirement.
Although a fair proportion of our work is on private land, we do cover events on the public roads, and do sometimes require to get from A to B in as quick - but safe - a way as possible. We have never covered or removed any of the emergency lights from either vehicle, as it's my understanding that we are using the vehicles 'for ambulance purposes', or for the 'transport of human organs' (which does include blood).
All our drivers hold advanced motorist qualifications, and the 2 bike riders hold IAM qualifications. All our vehicles are fully insured for blue light use, and carry public liability insurance.
The only time we've ever had an issue was in Newcastle last year when traffic police pulled our bike over more out of curiosity than anything else i think.
As far as I can see, there's no requirement in the RVLR that says an emergency vehicle stops being such when not actively engaged on the run.
We are actively considering seeking an Action of Declarator from the Court of Session up here in Scotland as to where our vehicles stand, and i'll obviously keep the forum posted about that.
I would finally say i'm all for bringing in a minimum standard for all blue light users, particularly in the ambulance sector, which i agree has more than its fair share of bad press over the years.