First off, it's not that far-fetched (see below). Second, it would have to be reviewed by someone at the RCMP firearms lab and a determination made. If it is clearly documented that the barrel was cut after manufacture then it would most likely be declared prohib regardless of how insane that is.
Example #1:
A number of years ago the OPP (I think it was) had a number of pump action shotguns that they sold off to the public as surplus. Those shotguns had started life with 18" barrels and were cut down to 14" by police armourers. Some time after they sold them off to the public the RCMP determined that they were in fact prohibs due to the barrels being cut down (by agents of the crown, no less) and had to be turned in for destruction. I think they even wanted the entire gun, not just the barrels in question. Some people lost their shotguns over it and I am not sure how it all turned out in the end.
Example #2:
The CZ858 fiasco that resulted in the prohib declaration years after they were imported came about because the receivers were determined to have been 'converted autos'. What happened was the receivers were originally assembled into select fire rifles but never shipped anywhere by the OEM. They were then broken down back into spare parts and stored for some time. After this the OEM re-manufactured the receivers (by machining operations) to be semi only and built the semi 858's that came here. After much time the RCMP decided those rifles were converted autos because some time in the distant past they had existed as select fire rifles in storage. Essentially they were collections of parts on a shelf and never saw the light of day, but they were still evil full auto receivers and must be banned.
The basic lesson is to expect the stupidest, most unreasonable determination possible from the firearms lab, regardless of the actual circumstances.
Mark
