Only other way I'd see to move around in Ent would be either the Engies' warps, or to be Gridded by a level 100+ Fixer. Unless they put these black guards at the sewer's north entrance as well, or it ain't possible to Grid someone this way (oh yeah, I'm talking 'bout the *Fixer* Grid here. Can't bring people there myself, so I can't check this myself)...
Oh well. We'll go to Reets, eh. That ain't such a big way to travel on
