Normandy was pretty well photo'd to death by June 44. The RAF had reference footage for the whole of France, any changes are going to get noticed in fairly short order, any changes will be picked up an analysed. Plus the French resistance had the railways thoroughly penetrated by 1944, any large scale transport of forces particularly armour will be reported to London in almost real time.
You would see a rapid escalation in Allied interdiction efforts against rail links beyond anything dreamed of today simply as all that gear in transit makes them easier to get at. They can't move much by night due to the shortening nights prior to the Summer equinox and road marching mechanised equipment just burns up fuel and will leave a trail of broken down panzers, armoured car and trucks across Northern France.
You would see a rapid escalation in Allied interdiction efforts against rail links beyond anything dreamed of today simply as all that gear in transit makes them easier to get at. They can't move much by night due to the shortening nights prior to the Summer equinox and road marching mechanised equipment just burns up fuel and will leave a trail of broken down panzers, armoured car and trucks across Northern France.