UHF RFID is often selected as a technology for mobile objects identification like vehicles in the toll road systems or goods on the conveyor belts. Such systems have unique properties, the most crucial is that each tag has only a limited number of attempts to be identified, and if the tag fails to transmit its EPCID it can become inaccessible due to the session flag alteration. However, most analysis in this area is devoted to the channel properties estimation and doesn't consider session flags alteration effects. The session flag alteration rules can be used by the reader to increase the number of attempts to identify a moving tag by changing the target flag value from round to round, or by switching its power to let the tags reset their flags. In this paper a new stochastic model for analysis of the EPC Gen2 protocol is proposed. The model takes into account a periodic target session flag alteration and power switching and allows to study the mobile tags identification probability. The channel is supposed non-ideal with a constant BER value. Numerical results show that target session flag alterations and power switching allows to significantly increase the mobile tags identification probability even under the high BER values. The proposed model could be used for the UHF RFID systems with mobile tags performance estimation and to analyze the efficiency of various tag querying scenarios.