Interesting - we use a different procedure here than +TSRA. Before departure, we are required to leave the flaps at 0 for deicing (DH8-400). The reasoning behind this is that a heavy crust of ice may or may not break before the flap system gets damaged if one tries to move them. So the flaps stay up and are only set into the takeoff position after treatment.
After landing, there are no considerations with regards to the flap system on the book. As has been mentioned, the spray from the main wheels will pass well below the flaps. The problem lies with the nose gear though: the radio altimeter antennas right behind the nose gear can and will accumulate much slush in some conditions, so the taxi speed is restricted in these conditions and a check for contamination in this position is required before departure (usually, quickly washing the mud off during deicing is appropriate). After an approach in severe ice, a check before retraction may of course be well advisable.
On the F70/100, it was different due to the low wing. After landing on a slushy runway, the flaps were not to be retracted above 25° during taxi. On the parking stand, one would then quickly wipe the leading edge clean, switch on the electric hyd pumps and wind the flaps in. Failure to do so could firstly lead to the flaps icing up in a position where no glycol could ever get and getting damaged and secondly win the culprit a free ticket to a one-way briefing sans tea or biscuits.