Yes, the mandatories will still be taken. The team will be charged a timeout...which is excessive. Upon resuming play, the opponent will shoot a free throw for the excessive timeout. Under NBA rules, following a T for excessive TO's the opponent is also awarded possession of the ball.
If a team only has a 20 left, they'd be charged a TO and lose their 20.
Correction: The 20 can not be used as a mandatory. Therefore, the earlier situation would apply