about the fat "migrating"... well fat never migrates like that. cells aren't going to decide to pack up and move to another area of you body. generally how it works is that if you are young you can change you fat cell count very easily, and they can be "moved" around the body as you lose weight and gain weight. it gets harder as you get older. Think of it this way, each fat cell is a warehouse, and sometimes they get abandoned, but they will still be there. in this way of thinking if you work out now pre HRT and really burn up your fat stores, when you start packing it on again your body MAY choose to use far more of the "female real estate" of your fat cell count. aka buttocks, hips, breasts, etc. That's pretty much how it works.
and yes, there are exceptions to altering your fat cell count, and no, cutting them off your body physically will not get rid of them. the body keeps track of how many emergency rations warehouses it wants to keep, and will rebuild them.