Yes, there is a common lounge used in BLQ. If I am correct, it is known as the Marconi Lounge. Easily seen as you enter the departure area. It is used by most airlines, ie: SkyTeam, *A and I guess to an extend OneWorld (did see the Finnair sign). It is operated by the airport itself. It is nothing to really shout about, just a built with 4 walls, with some snacks and drinks. There is one computer with internet, but I guess it would be down as it is rather old. The main attraction there is the tv. If there is no one there, you can freely change channels.. however, if there are other guests in there before you...

The lounge dragons are not too bad, though the only bad one is the guy (not sure if he is the only one working there ) The ladies are ok. If you are flying Y and going in with ur FTL, if it is the guy, he will like really check if you are "eligible" to enter his kingdom... the ladies are rather ok with it. You will however, get a stamp on your boarding pass. I am not sure if this is true or not, but accordingly if you have this stamp on your boarding pass, you can use the express lane at the security lines as it can get rather busy at times.

Hope this info answers your question.