Yeah you enter one, but pole arm doesnt say anything specifick about teleportation.. so it isnt an specifik rule that ignores the teleportation rules..
And.. teleportation is an interruption, but you cannot interrupt something that is not there because the one with the defender doesnt know where you will appear until you are there.. and then the action is already done..
Which means there is a situation in which a person with polearm gamble can make an OA against a person teleporting. That person must be in a non-adjacent square within reach and teleporting to an adjacent square.
Now the little guy is shocked but as I said he thinks he is bigger then he is so he attacks John. As expected from a guy names John Wayne he shacks of the attack like it was nothing. He lifts his spear and strikes the kobold with a flash of martial power the likes few could match. Now are kobold friend is not too bright but he is fast he thinks he might have a better shot if he shift over one square. Now John can only hit him once so he swings with another AO.

(Dungeons & Dragons)
Rulebook featuring "high magic" options, including a host of new spells.