Mandatory OT

I work in a hospital where doing overtime is required. We have been doing this for years, but the past year has been overwhelming. Our hospital hasn't been hiring nurses for about a year. (we are finally getting a few agency till we hire a few nurses). I work in a mixed ICU. We do not have a float team. We are a level 2 trauma center. We also have VAD, ECMO, IABP's, CRRT, and rotoprone patients. We are not a little hospital that sends pt's out, we are a hospital that takes other ICU's critical patients.
Our charge nurse always has an assignment of 1-3 patients. So they are rarely able to help staff if a patient goes bad.

It's not the kind of unit where we should be tripling up assignments.

I was wondering how other hospitals mandate nurses. Is it a policy for the whole hospital or is it unit specific.

Here are a few specific questions:
1. how much time constitutes mandatory overtime (our union rep says 1 minute, our manager says anything over 4 hours)

2. can you get mandated if you voluntarily pick up an extra shift? (manager said no, union rep said yes)

3. if you voluntarily work 16 hours the day before, can you be mandated the next day? (manager says no, union rep says yes).

I know that mandatory overtime is illegal, we submit the papers. We just need to deal with the problem at hand. Any suggestions for agencies to contact would also be helpful.

Thanks for your help.
Mandatory overtime is against the law in Texas (for nurses). We have learned to plan better. Also, the law states emergency situations are exempt, so if an ER patient needs surgery, then someone may have to stay over to assist the pm team.