They wouldn't be much of a problem if not killed and multiplied..i.e. the one or two that show up could be lured away? Possibly handle ig by suggesting a law in Trolls Bane not to kill them, would stop it sometimes except for the lawbreakers. Greenbriar has/had a law not to kill the rabbits in town.
There are some instances the mummies have made for some very interesting RP also, looking at the other side of the issue. As far as an RP issue, I guess up to your char..mine still hasn't figured out why mummies jump up from the river.