I installed VEMS on M50B25 equipped E30 carbio last summer and it worked like a charm even without overlapping dwell. It's a non-VANOS engine though I recently installed VEMS on Mercedes 190E with 3.2liter 24valve engine from 1996 S-class that has some sort of "variocam". It's a simple on/off type and retards intake cam below 2000 rpm, then goes normal position and retards again after 5000 rpm.
We dyno-tuned the car without it (255 hp/380 Nm) and next session we're going to play with the cam timing as past 5000 rpm torque and power fell off like a rock without the cam retard.