Eltonioni, Yes I am a current fATPL on the RJ series (tarted up 146
)
I do seem to remember they descend at a given rate but bearing in mind they won't be moving forward at anywhere near the same speed they were when they left the wing, and with wind and perhaps thermal activity, you could find a situation where you catch the vorticies up.
You are correct, with proper seperation wake turbulence shouldn't be an issue, but the question that the Turkish Pilots Union (TALPA) is raising is whether the proper seperation was maintained? But the responsibility ultimately falls onto YOU the pilot to manage wake seperation, the question could be did the crew take into account the heavy wake vorticies catagory of the preceding B757?
(of course assuming there even WAS a B757 preceding...or that wake seperation was inadequate)