Thats a terrible thing to happen, and I'm sure has done nothing for the morale of everyone else who works for the company.
It is so un-professional, that it does sound like a sick joke.
Surely, they must have got something in writing, stating their redundancy payments and other information they will require for official confirmation of them losing their jobs.
Years ago, a company I worked for, fired a girl with a fax, and I thought that was bad enough, but a conference phone call, is as insulting as it gets.