From 320 FCOM (CFM's)
CAUTION
On taxiways, the use of reversers, even when restricted to idle thrust, may have the following effects :
-The engines may ingest fine sand and debris that may be detrimental to both the engines and the airframe systems.
-On snow covered areas, snow will recirculate into the air inlet, which may result in engine flame-out or roll back.
Except in an emergency, do not use reverse thrust to control aircraft speed while taxiing.
I know the thread was with ref to NG's, but thought Airbus's take on it could be of interest.