After a public challenge and a miserable failure I had to try again and I think the photos are just a bit better and the place was better organized (being so close tot he Christmas).
Overall I am still unhappy with the photo session and I still think the city officials did a shitty job, but Saturday night on location a big glass (400ml) of boiled wine temporarily changed by view about the world and life.
But let's try some learning from here: taking night photos (or just with not enough light) your camera will use a large ISO value, so it don't need a very large exposure time (you can't afford a long exposure if you shoot moving targets and/or your camera isn't fixed on a tripod).
The downside of a large ISO value is the addition of a lot of unwanted noise and you will surely want to post-process a bit and try some corrections. A good tool for the job is GREYCstoration, a GIMP plug-in (yum install -y GREYCstoration). I should have used it in all the photos, but being computation intensive it take a lot of time on 12 MP photos, so I applied the treatment only to some.
PS: I still feel pity for the poor reindeers, they looked really unhappy.