Location: Malta, the sunniest Member State to be!!
With regards to the VRT, yes it will fail. What year is it? The only way ule get away with it is if the car is a pre-1996 model, or if you have an extremely friendly VRT Station
I'm not an Alfa mechanic, however seen from the fact that many after-market exhaust manufacturers make catalytic replacements that look like the traditional 'cherry-bombs', and that the only warnings they give is that such a replacement is not for public-road use, I should assume that its pretty safe to remove.