yes it can. we used to have an AT group that played, but we stopped after a while
just use the multiplayer functions and import (or create new) characters, or players can take control of the characters you encounter throughout the game (imoen, jaheira, minsc, etc.). standard host/client setup like so many other games. make sure you have the right port open. all players must be running the same version.
even though BG2 is a single player RPG, the multiplayer is surprisingly good i thought, since i played with a consistent set of people.