On the textual question the answer is no. The only variant I could locate in
this verse is EPI/EIS which is noted in NA 26/27. The extant Papyri do not
contain this passage. The reading TA ORH seems to be uncontested. I was only
able to check three commentaries H.A.W. Meyer, A. Plummer and W.
Hendriksen. None of these even mention the plural.
TA ORH can be seen as a collective idea but I am sure that is not what you are
driving at. What are you driving at?
Where I live, Three Tree Point, if some one says: I am fleeing to the mountains
you don't have a clue where they are going. It could be west, north, east or
south. If some one says I am fleeing to the mountain, you know exactly where
they are going. The are going south east about a hundred miles. In this
context Jesus tells those in Judea to flee to the mountains. Plummer
suggests that they would have no problem understanding this because it was
a standard tactic of the Jewish revolutionaries of Jesus day to hide in the
hills of Judea in the caves. (c.f. a good translation of Josephus' The Jewish
Wars, or read it in Greek if you are able).
Clay Bartholomew
Three Tree Point