Per the Mavericks:
ROUND ONE GAME SIX PLAYOFF TICKETS ON SALE TONIGHT
Contingent on Mavericks Winning Game 5
April 28, 2015 (DALLAS,TX) – Contingent on the Mavericks winning Game 5 in Houston this evening, tickets for the third Mavs home game of the First Round of the 2015 NBA Playoffs will go on sale TONIGHT, April 28th at 10:00 p.m. Tickets will only be available online at mavs.com. There will be a four (4) ticket limit per game.
The third Mavs home game (Game C) will be Thursday, April 30th. Tipoff time has not been announced, but will be posted on mavs.