Disclosed are methods and systems for segregating user equipment devices (UEs) among carriers to help facilitate operation in lean-carrier mode in which a base station (BS) engages in a reduced extent of reference signaling on a particular carrier. In practice, the BS may operate in the lean-carrier mode when bearer data is not being communicated on the particular carrier. Given this arrangement, the BS may identify one or more UEs, of a plurality of UEs served by the BS, based on each UE communicating bearer data less frequently than a threshold frequency of bearer data communication. And the BS may serve just the identified UEs on the particular carrier, thereby increasing a probability of the BS operating in the lean-carrier mode.