This tradition has been extended into an annual festival in December, Fete des Lumieres, and appearantly during that three day festival the city is like a fairytale with candles, illumniated buildings, fireworks and light signals.
Unfortunately I wasn't here yet in December (well, I was in South America then, so that's hardly unfortunate...) but it turns out that the city has cool light projects year round.
The most important buildings and bridges are illuminated at night in various colors. It is really quite cool....
(As you can see Lyon has its own tiny "Eifel Tower")