I doubt E5 ever makes it to 148W. I bet this is just to keep the FCC happy that they are trying to retain their transponders at 148W. Compounding problems, 148W is an orbital location that requires more station keeping manuevers than most, due to the earth not being a perfect sphere. If E5 was left to drift on its own, it would gradually move to 105W. They can move it to 148, but it takes more energy going west, even if they just want a slow movement.
See the attached chart. The points at the bottom are stable, ie no east-west station keeping is needed. Everywhere else, a slight adjustment is needed to keep the satellite from drifting. 148W is at the top of the third hump. The numbers on the bottom axis are degrees East, so to convert to degrees west, do 360-x. Ex. 360-148 = 212E.