The only problem with wearing an item of reflective clothing that is different to what the organizers provide you with is, it stands out like a beacon on a night even amongst a group of other riders as being completely different. The officials on motorcycles would not have to come looking for riders wearing non conforming reflectives, the riders doing so would present themselves nicely in the beam of the motorcycles headlight and if they are having a bad day, may stop you, probably unlikely, but you never know. In 2015, there was a rider on a motorcycle who was stroppy with riders enforcing that they should be wearing them well before dusk, I fell foul of him myself and he had 2 or 3 goes at me before I decided I better put it on before I got a time penalty, as it was hot and about an hour or more before dusk, I just took my jersey off and wore the reflective till it cooled down.