From far far readings months ago (at the beginning of the AF447 drama) it was noticed this plane was equipped with some kind of EPIRB but they do not function AKAIK by what was posted in this forum times ago.
Methink it's a legal requirement for have this kind of EPIRB aboard airliners.
406Mhz ELT's are usually installed on any large transport these days. No idea if thats what the AF had fitted but certainly what BA uses.
The have a foam float around the unit but for it to be effective it first needs to break free from the fuselage and reach the surface.