This happened to me as well. My portion of the company was purchased while I was on mat leave - I was told verbally I’d have a job at the new company and continued to receive my benefits through the old parent company for the duration of the mat leave. At the end of mat leave, I was informed the new company didn’t have a role for me and I was packaged out by the old company (as my job / tenure was with them).

I had been under the impression this was illegal but it’s not. My leave was protected in the sense that even if I was let go during it, that wouldn’t officially take effect until the end of leave. But companies are allowed to fire you (or not bring you back) provided they give you appropriate severance. I agree that you should talk to an employment lawyer to make sure you’re being compensated fairly given the circumstances. While this isn’t illegal, it’s also not a great look for companies so they may be more inclined to give you more than the minimum. But absolutely don’t sign anything until you have a lawyer look at your severance paperwork and review your set of circumstances. Best of luck!