Well, there's no trite law as to whether what charges are "supposed" to be levied on the consumers by these ISPs. It's all stated in their contract and you've agreed to them upon signing up for their services so if they want to levy such charges then you will have to bound by it. Plus, this is a request made by the consumer so it is "additional work" to them.

But generally, if you asked me, ISPs shouldn't charge for relocation fees because technically speaking, they are not physically relocating the services, just merely diverting the flow. Base upon the law of reimbursement, unless the ISP has incurred costs for the relocation (travelling, wiring etc) then it is prudent that we reimburse to them such costs. Other than that, I don't think it is fair to levy any charges on the consumer especially to the ones who remained faithful to them for several years.
The last I heard (in the month of October) is that there's a few units left but they are all facing undesirable directions and big units only so unless you have no preference then I'd suggest you shop around the market. There are quite a lot of people letting go units in Block A.