I believe all of the Richmond talkgroups are simulcasted on the Chesterfield site by default (either that or Richmond subs are constantly affiliated to Chesterfield), so if you're within range, it may be worth a shot to see if it's only Richmond's cell or if it's a scanner issue.
Only certain TG's are simulcast between the zones. Generally those for police, fire & ems dispatch, and possibly fire/ems response tacs. I don't think that Colonial Heights simulcasted outside the Chesterfield zone unless a vehicle headed up toward Richmond.
Last I surveyed this, police surveillance, fire admin, dog catchers and dump trucks would only be broadcast outside their zone if a vehicle using that TG affiliated with a site outside its zone. I think that University of Richmond PD may also be in this category, which is pretty interesting since they border Richmond, Henrico and Chesterfield. I've caught them on Chesterfield in the past.
Even so, your idea should work find for the OP if he's listening to Richmond dispatch TG's.
73/Allen (N4JRI)