Does my employer need to offer us severence pay?

My employer, AEP, is selling my power plant to another company Lightstone energy llc. As part of the sale, the employees stay with the plant. However, those of us that would like to stay employed with AEP are not allowed to apply for any jobs within AEP. When asked, HR says that it is part of the agreement with Lightstone Energy. The CEO of Lightstone, John Adams said that, they Lightstone, did not request this provision of the sale. I received the following statement from HR; I wanted to send a note on your JOBS interest. Big Sandy will not be able to consider due to the employment you currently have with the Waterford Plant and it’s Sale. The employees from Gavin, Waterford, Darby and Lawrenceburg have this restriction. It seems to me, that if AEP will not allow me or anyone else transfer to another facility, because of this sale, then they should compensate us with a severance package. Also, I fall 5 months short of being eligible for the retirement medical plan within AEP. I would really like to continue employment with AEP, but they will not allow this to happen.