I fail to see the point of the AMS route, VG offer an excellent service on this route which is very frequent and reasonably priced and KL caters for those who'd rather avoid LHR and use AMS as their hub (or like to collect FB miles).
BA would be competing with VG on point to point traffic and with their increased frequency of service why would anyone choose BA apart from to earn miles (on expensive fares so puts VG at a price advantage) or some allergy to the Fokkers.
I personally prefer the F50's to the RJ's (even the LX ones that have a nice comfortable Y config), KL's service on this route is adequate (and I've always found the FAs to be good on this route - 6 cans of Heineken last time, the hint is to sit in the back where they store the trolley and they'll give you more!) and VG's service is better again. I love the feeling taking off in the Fokkers on the short runway in LCY.
Although competition is usually a good thing - and VG certainly made KL improve, I think 3 operators LCY-AMS is just wasting capacity at LCY, it's good to see new destinations being tried like WAW and BCN and perhaps could have been a good idea to put more flights on popular routes that don't have a frequent service such as NCE.