There are situations where the fuel in the wing fuel tanks are below the freezing temperature after landing, then if there is any condensation on the wing, ice forms on the top of the wings, even if the OAT is above 0c.
An American airlines MD-80 had this happen, the wings were not de-iced, because no one noticed the ice and as the temperature was above freezing no one expected that the wings would ice up. After takeoff the sheets of ice on top of the wings broke off and were ingested into both engines.
One engine failed and the other engines lost some of its power, the Captain was able to nurse the MD-80 around to where he could land safely.
Some aircraft are more susceptible to this than others. I saw C-141s being deiced at McGuire AFB one night and the OAT was +10c. Never the less, the wings were being sprayed with de-icing fluid. More for ice prevention rather than ice removal.
Now, why the tail was being de-ice on the subject aircraft mentioned on the first post, I've no idea. Unless of course the aircraft had accumulated surface ice/frost from spending the night on the ramp. Even if it is frost, it must be removed before flight.
Better safe than sorry.