I have heard this for a G-reg scenario; both being G-regs and the donor having a valid CofA. Last time was from a Part 145 (EASA+FAA) owner. Never seen a reference though…
It does seem strange since after the removal of any nontrivial item the donor aircraft will cease to have a valid CofA approximately 1 microsecond after the said part was removed from it 
So…. logically….. a maximum of one item could ever be removed from such an aircraft, yes?
IMHO…
Could this mean instead that having a valid CofA for the donor aircraft makes it unnecessary to get a Form 1 for the part being transplanted?
I think it does, but why?
In the FAA system, and A&P or an IA has (in most circumstances) the authority to declare an item as airworthy. So e.g. he could unscrew a door handle from a crashed or long-abandoned PA28, inspect it, and screw it onto another PA28. He needs to be satisfied it is not a counterfeit part, which would be achieved by establishing that the donor aircraft is a real Piper-made PA28 and not a chinese fake (as if the chinese ever faked a PA28, but you get my drift).
But in the European system, he can’t do that (overtly ); he has to process that door handle through a Part 145 company (whose authority includes the inspection and recertification of door handles) and get a fresh Form 1 generated.
I can understand the (perverted) reasoning in the para above, but can’t see why that donor PA28 needs a valid CofA. The door handle is no more likely to be airworthy.
This whole thing is a huge grey area. A lot of planes get broken up, some because they were abandoned and some because they had e.g. a forced landing which wrote them off, and the parts get sold off to various people, no questions asked… I know of a complete G-reg SEP (a few years old, 400hrs) which had been broken up over the last few years and almost everything was sold off in that way. Of course it didn’t have a CofA.
As Ultranomad indicates, in most cases you will need an EASA Form 1.
EASA Form 1 for these used parts can only be issued by Part 145 or subpart F company, on the latter you would get a form 1 with limitations. These companies are either can use it within their organisation (removal and install within the same company, and using correct procedures this wouldn’t require a Form 1), for installations by or from other companies or mechanics you will a Form 1. Some, not all companies can issue a Form 1, depending on their capabilities.
There is no suchs thing as yellow tag under EASA.
I can see the reasoning for the Form 1, but what about my original Q?
removal and install within the same company
What specific concession is that?
Answering the question, the part needs a form 1 before it is fitted. Take this to the extreme, I’ve swapped-out/in engines; all that is required is a Form 1 for the parts or, in the case of the engine, the logbook goes with it.
Where is it defined that carrying through a logbook avoids the need for a Form 1?
It is defined somewhere in Part 145, and it has nothing to do with logbooks.
There are procedures relating to loaned components. There is a provision allowing for a maintenance organisation’s own “internal release certificate” instead of a Form 1 when a part is borrowed from an aircraft maintained by that same maintenance organisation.
