Now, if this were France or Holland, where Squatters Laws have been existence for hundreds of years, we could all just go occupy the place and make it nice. I'm serious.
The right in Europe to make use of abandoned space goes back centuries and exists to prevent the kind of private property abuses happening on Garfield Place; it's a right that assumes a common responsibility in any given community, an idea that we are all stewards of each others' quality of life... This idea is generally not too important to real estate "moguls." (Hooboy, I'm really feeling the whole communo-fascist-socialist thing today.)
So, if Garfield Place was somehow magically transported to The Netherlands, this little problem would be cleared up in a week. The rule in Holland is that if a building has been unoccupied for 12 months, you just need to get inside, set up a bed, a table and a chair, and voila, home is where you squat (the tricky part is getting inside, as breaking in is technically illegal). It's also considered politic to send a letter to both the owner and police, inviting them to come and see what you've done with the place (I can only imagine the pleasure Garfield Place residents would take in writing such a letter to their absentee enemy).
Things are perhaps a bit tougher in France (where I had the pleasure of squatting in my, err, younger days), though there are official avenues available to squatters who really make something of their abandoned conquest (specifically, subsidies for artists and other contributors to the community). The guidelines for squatting are not dissimilar to The Netherlands, with a certain number of people required on each floor of the squatted building in order to legitimize the claim. But, unlike Holland, you do not want to invite the police in, as once they're inside, they can pretty much do whatever they want to kick you out.
Sadly, there aren't really any rules for squatting in New York (you just kind of have to break in and hope to stick it out), so I don't suppose any of this is applicable to the Garfield Place fiasco... One can dream, though.