Sewer entrances/exits on IC side should work justlike outlaws refugess do.
A player should be able to enter it no matter if he is currently in combat or not.
Its obvious that first faction that will beg to IC will try to camp other factions sewer entrances killing every single player who tries to enter it.
Also sewer entrances should be made this way that there is no loading screen upon entering it (just like some of the instances work already). The reason is obvious, from 10 sec to 3 minutes of infinite loading screen during which you can be killed in 10 ways possible and many more