The thing I always wonder about in French rail strikes is that there is always a skeleton service running despite the strike, with notices posted in the stations showing which trains are running. Once I was scheduled to leave Paris for London via Boulogne-Folkestone (pre-Eurostar) and found on the preceding afternoon that some trains were running and that my intended train for the next day had run. The next morning I was assured that if the train showed up on the board it would run; it was on the board, and it ran, although practically empty--evidently any locals who had planned a trip just shrugged and postponed it. The same applies during a Metro strike--there are signs in the stations saying things like Line 2--67% normal service and Line 6--50% normal service. Whether it has to do with different unions I never found out.