Working with Shimano and SRAM groups on my bikes I can say that Cable Housing are the same. Usually Brake Cable housing is 5mm in diameter and Shifter Cable housing can be either 4mm or 5mm.

Shifter Cables are the same for both Road and MTB. The ends look like little barrels. Brake Cables are different. Road Bike brake cables have mushroom like ends where as MTB brake cables have barrel like ends.