Set up one very controlled exit point, where the Commies can be processed, interrogated, then transported in shackles to the waiting C-130's for movement to Gitmo for a nice long tropical resort vacation.
the anarchist live on the streets and that park, but NOT in the building that adjoin those streets, which are private residences and businesses, so not really possible to cut utilities or even cell phone service ...
what WOULD be possible is to block the ends of all of the “occupied” streets with large dump trucks parked end-to-end with a single egress point as you suggest, but NO ingress or anything or anybody ... it prevent egress, police would have to form a line along the outside of the truck barriers, and another group of police would need to be stationed a block away to surround any trouble makers attacking the barrier police line ...
moreover, once ALL of the anarchists have been evacuated, the entire area would still need to remain blocked off to prevent re-entry AND to repair all of the vandalism that had occurred, including seal-coating all the streets to obliterate the street graffiti, and removal and/or painting all graffiti on building facades ... and the East Precinct would be completely restored to full functionality ... all of this has to be done before removing the barrier ...
additionally, police would have to be alert to subsequent attempts to reform the anarchy zones and move in and nip them in bud right off the bat as other cities throughout our nation have done, thereby squashing anarchy zones in the early fetal stage, when such squashing is mostly easily done ...