From the information provided, there is no yes/no information that the firearm was legally deactivated. If it was, there would be a papertrail from the gunsmith to the RCMP labs and to the owner. The cops don't like people breaking welds they've inspected and making guns live. It is the sort of thing that basement tinkerers and crooked gunsmiths do.
http://www.rcmp-grc.gc.ca/cfp-pcaf/bulletins/club/bulletin12-eng.htm
If the welds were done by Cousin Billy-Joe Sixpack and his $200 Princess Auto snot spitter, the effect is still the same. A firearm which was rendered safe for its owner is being rebuilt. The expectation seems to be that new owner would want to fire it. That means it will be reactivated. I don't have the references at hand, but making firearms is one of those activities layman should be cautious about. Not that I give a $hit about someone's engineering abilities, it is (IMHO) their actions expose them to charges of manufacturing firearms. The regs are there because of unprincipled handymen. Gouging out the plugs might seem easy, but bullet two of the reference, has language that puts the onus on the person doing things,
"The new standards will not affect the status of firearms that have already been deemed to be deactivated unless there is evidence that the firearm has been, or could easily be, reactivated."
So, I'm the voice of caution that the new owner go through a properly papered gunsmith. Sure he might chose to be a rugged individualist, but stories of reactivated deactivated firearms don't look good on the hobby. Nor does ignorance of the letter and the spirit of the law.