That's utter bilge I'm afraid.
BT Wholesale, Sky, TalkTalk, and C & W/Vodafone are the main Communications Providers (CPs) at the exchange.
You are connected to a BT Wholesale port>>card>>MSAN at the exchange and a migration between any of the hundred or so ISPs that use BT Wholesale requires no moving or physical change of your connection. It's all done in the routing software. Swaps between hardware only occurs during migrations between the four above. (Zen is a special case where things are a little unclear).
From the exchange your connection disappears into the BT Wholesale "Cloud" of WBC/WBMC. At the other end of that cloud is where things split out between the various ISPs, via MSILs. (Sorry about the jargon but it's time for me to find something to eat

). I've got a lot more explanation on
this page.
If I've understood your connection correctly it will be IPStream Connect, explained on that page.
It is MSIL capacity and deeper into the ISPs' own networks that capacity problems normally arise. I'm not aware of any that would cause your issue 24/7, so as we think we have ruled out anything your end it's almost certainly a fault at the exchange. From the exchange onwards your traffic is no longer running on hardware unique to it. An analogy is that it becomes one fish of the shoal moving in the same water pipe.
Plusnet use WBMC for 21CN traffic, whereas BT Consumer may be using direct access to the world through BT Wholesale for that. Not even going through the WBC/MSIL route. What BT Consumer do with IPStream Connect I don't know.
So your friend is either talking out of the back of his head, or he is confused about where the split of the traffic takes place. It's at the MSILs.
Having said that, it is likely a full reset of your line will be done when your migration takes place. If there is anything screwed up in those settings, (similar to how we sometimes need to do a factory reset on a router), then your problem may go away. Let's hope so

. But it won't be because your connection has been physically moved.