In this paper we study a non-stationary Markovian queueing model of a twoprocessor heterogeneous system with time-varying arrival and service rates which was firstly investigated in [21], see also time-dependent analysis of this model in the recent paper [20]. In general, non-stationary queueing models have been actively studied during some decades, see, for instance [3,5,6,11,16,18] and the references therein.In the paper [20] the authors deal with the so-called "time-dependent analysis", in other words, they try to find the state probabilities on a finite interval under some initial conditions (as a rule, initially, the number of customers in the queue is zero), see for instance [2]. Another approach is connected with the determination of the limiting mode, see [1].Essentially more information about queue-length process can be obtained using ergodicity and the corresponding estimates of the rate of convergence. A general approach to obtaining sharp bounds on the rate of convergence via the notion of the logarithmic norm of an operator function wsa recently discussed in details in our papers [23,24,25]. The first studies in this direction were published since 1980-s for birth-death models, see [14,15]. In [23] we proved that there are four classes of Markovian queueing models for which the reduced forward Kolmogorov system can be transformed to