A lot has happened since May 18, when the city teachers union first filed a suit against the Department of Education’s plans to close 22 schools and co-locate 17 charter schools in the 2011-2012 school year. There were mass protests, low-key concessions, more lawsuit threats and signs of settlement.

There was also a request for a preliminary injunction to place an immediate halt on all interim co-location and school closure plans, which is what today’s court date is about. In these preliminary hearings, Manhattan State Supreme Court Judge Paul Feinman will listen to arguments and decide whether or not to grant the request.

Here is a rundown of the latest news and analysis of the lawsuit and its implications for how it will affect school co-locations and closures for the upcoming school year.

1. What’s a preliminary injunction?

A preliminary injunction is an early court order that requires the defendant to either proceed or cease with a specific action. In today’s hearing, Judge Feinman will decide if the DOE and co-locating charter schools can proceed with plans to move into district school buildings until a final ruling is made. The injunction — if granted — would halt any construction, renovation or facility upgrades that the schools planned for its co-locations.

The key to winning the injunction for the UFT will be to prove, among other things, that the co-locations are irreparably harmful in the interim weeks (as opposed to when the school year begins) while the lawsuit is pending. They will also need to prove a high likelihood of ultimately winning the case.

2. What’s at stake?

This is a preliminary hearing, but its timing in the middle of June means a favorable ruling for the plaintiffs would deal a serious blow to the charter schools’ hopes of co-location next fall. An injunction — if granted — halts any interim renovation plans in the schools’ future buildings while the lawsuit is pending.

Technically speaking, the charter schools’ lawyers would be able to appeal, but as a matter of practicality — with less than two months to go before the school year — it would be challenging for the schools to plan their move.

At least seven charter schools listed in the suit would not open next school year if the injunction is granted today, according to court documents. The other 10 schools, which are part of well-funded networks, could raise money and find private space given the time period.

If the relief is rejected, the charter schools “would still be breathing,” one lawyer said. “It’s not a complete win, but it’s a significant win.”

3. The defendants table just got a little more crowded.

On Friday, four law firms filed a motion to intervene in the lawsuit. They will independently represent the 17 charter schools whose 2011-2012 co-location status is up in the air next year. They will exclusively focus their representation on the co-location part of the lawsuit. The lead point in their argument will be that the revised space-sharing plans, most of which will be voted on at next week’s Panel for Educational Policy meeting, rendered the lawsuit’s complaints moot.

The firms are heavy-hitting corporate practices, all of which are representing the charters pro-bono. They are Kirkland & Ellis LLP (New Visions High School, New Visions School for Advanced Math and Science, Teaching Firms of America, Invictus Prep), Arnold & Porter LLP (Upper West Success Academy), Paul, Weiss, Rifkind, Wharton & Garrison LLP (Bronx Success 1 and 2 and Brooklyn Success), SNR Denton (Explore Excel, KIPP Infinity, Harlem Children’s Zone Promise Academy 1 and 2 and East Harlem Scholars).

4. But don’t forget about the school closures.

Although much of the public debate has surrounded the contested co-locations, the lawsuit is also seeking to prevent the DOE from closing 22 schools this fall. That will likely take up the majority of the hearing this afternoon. The UFT will argue that the DOE failed to fix its broken process for closing schools since last year, when a lawsuit reversed a plan to close 19 schools.

5. Yes, there will be public demonstrations.

Parent groups from both sides of the aisle plan to camp out inside the courtroom lobby as well as outside of the Manhattan State Supreme Court Building at 60 Centre Street.

Neither gathering is likely to match the size or intensity of the Harlem protests that took place several weeks ago. A release sent out by charter school advocates said that parents and school leaders plan to “discuss” the impact of the lawsuit today.

The UFT responded to the charter school advocates’ organizing by calling on parents and other supporters of the lawsuit to come out as well.