I moved out of the DC suburbs under a year ago, so I feel qualified to comment on why the government of Washington DC and the OccupyDC occupation are getting along so well. So I'm going to share my unique insights with all y'all.
There are two major reasons, IMNHO. The first is the unique relationship that DC and it's residents have with the Federal Govenment, the second has to do with .... the reality of the type of folks who so often get elected in the US.
I'll start with the fact that Washington DC and its residents do not have any federal political representation ... and that the Occupy movement is focused on the relationship that corporate money has on ... the federal government. DC government can't even make their own laws without 'review' by Congress. Washington DC is a not-represented US colony. As a result, most of the city government is more than happy to help folks pressure the Federal govt about ANYTHING. Poke them! Harass them! DC Govt will stay out of your way as long as you don't cause any more problems than the constant federal motorcades cause. DC is used to protests. They've been thru' calm ones, mild ones, and everything in between. After the WTO ones, OccupyDC is a bunch of scouts camping out in a park. The police like protests, in my view. They justify keeping lot of police hired, and dealing with them is FAR safer for the police than dealing with criminals and far FAR safer than going on a domestic violence call. Back under Police Chief Ramsey the size of protests were routinely overestimated, the better, IMO, for the police to ask for more money from the city.
Sidebar - for some protests under Ramsey I'd go into DC and watch them, taking the Spawn and teaching him to estimate crowd sizes. I'm pretty good at crowd size estimation, in my opinion.
The other major reason that OccupyDC and the Washington DC city council are getting along is .... Sigh. We once again have a mayor who is under investigation of possible criminal wrongdoing. Having protestors in town and having the press give THEM attention takes media attention off of him. Personal political power is at stake, but only if the residents follow the story (and care about the story). Even if there is enough evidence to prosecute him, even if he's convicted, none of that matters. What matters is voter memory. The less the press carries the story, the shorter the memory of voters.
So, those are, in my view, the major reasons why OccupyDC is smiled upon by the DC city council. They see it as something that can only help the status of the city and/or their careers.