I'm sure others will chime in. I have a 255/275 setup with my Blizzak LM60 winters on the stock ZCP wheels. I currently am not using spacers, but I ran this setup last winter along with 12.5mm spacers all around. No problems up front, and only slight rubbing in the rear on big suspension compressions over certain dips/bumps. The Blizzaks have a fairly rounded shoulder, though, and these same spacers and ZCP wheels with the square-shouldered OEM Pirelli PZeros caused a lot of rubbing in the back. So the success of it probably depends on the shoulder design of the Yokohamas. I don't use the spacers in the summertime with my 19" GTS wheels and 255/275 Michelin PSSs because I'm pretty sure they would rub in back.
A 255/275 setup on 19" wheels is a very common upgrade, but maybe not with spacers...
IB E90 M3 ZCP returned to BMW FS