We consider an exponential queueing system with
multiple stations, each of which has an infinite number
of servers and a dedicated arrival stream of jobs. In addition,
there is an arrival stream of jobs that choose a station
based on the state of the system. In this paper we describe
two heavy traffic approximations for the stationary joint
probability mass function of the number of busy servers
at each station. One of the approximations involves state-space
collapse and is accurate for large traffic loads. The state-space
in the second approximation does not collapse. It provides
an accurate estimate of the stationary behavior of the
system over a wide range of traffic loads.