I don't know if the HP switch supports any NAT / tunneling features, but I wouldn't rely on that as a good means to move your servers in a hitless manner. It's fine technology, but the HP switches aren't so great.
Your transit providers are unlikely to help you move just a few IPs, especially if you aren't actually their direct customer, but are buying bandwidth from your datacenters, who then buy from transit networks.
Ok, What I meant was, if you have same datas you can basically keep one server on datacenter A and move other server to DataCenter B then you can do IP forwarding.