can anybody tell me, when I eventually get a vehicle with a digital tacho, my vehicle is used round the yard as a shunter at night, when I start work in the morning is all this data dumped on my card as the vehicle will not have a card in whilst it is being used at night.
Welcome to TruckNet.
I can re-assure you that no data will be transferred in the circumstances you have described. 
I often get into a motor and as I insert my card I notice the display screen reads “driving without a valid card.”
Then I know that someone has moved it during the night, perhaps to load on a different bay, or maybe to go across the yard to top-up the trailer bellytank and set the fridge running for a few hours before I get in - (can’t be bothered plugging it in, some of the loaders 
)
many thanks, you hear all sorts of scare stories and this one crops up frequently, load of fuss about nothing.