So..I'm being trained to take on after hours systems support coverage and weekend coverage. Since most of those who were let go were doing the deed, there's nobody else left to do it.

So when I asked if we get compensated for being on call and the after hours additional work we do, they just laughed.

Then why do it!
If you have their response as an e-mail?
Collect documentation.
Unpaid work is criminal!

it’s not good.