There’s good news and there’s bad news this weekend (Friday, June 16 at 11:45 PM to Monday, June 19 at 5:00 AM). The good news is that there will be 4/5 service in both directions at Borough Hall, so those traveling to or from Manhattan’s East Side no longer need to take circuitous routes. The bad news is that there will be no 2 or 3 service to or from Brooklyn, so no service on the 2/3 platforms at Borough Hall and no service at all at Clark Street. To partially make up for this, 5 trains, which normally don’t serve Brooklyn on weekends, will be coming to and going from here. For those traveling to or from the interior of Brooklyn, 4 and 5 trains will be making the 2 and 3 stops. To complicate matters further, there will be no R or late night N train service from Manhattan to Court Street, as the Brooklyn bound R and N will be diverted to the Manhattan Bridge between Canal Street and DeKalb Avenue. The MTA suggests taking the R or N to DeKalb and catching a Manhattan bound R or N back to Court from there. You might do just as well taking a 4, 5, A, or C, all of which should (barring unforeseen events) be running more or less normally.
The following work week (Monday, June 19 to Friday, June 23) the only planned difficulty is that the Brooklyn bound N train, which replaces the R train late at night, will be diverted to the Manhattan Bridge between Canal Street and DeKalb Avenue, so there will be no service from Manhattan to Court Street each night Monday to Friday, 11:45 PM to 5:00 AM. N trains running to Manhattan should be providing service as usual. R trains will be running normally each day, so there will be service in both directions at Court Street except during the late night hours.
For planned service changes that may affect travel on other parts of the system, either during the weekend or the following week, see MTA Info or The Weekender.