The following information has been sent to me by Ian Longworth. I have not yet made much head way myself in getting information locally, but Inspired by Ian's email I will redouble my efforts!!!
From Ian
The system is fairly modern and is believed to have opened on 29th October 1987. We suspect a product of Russian aid. No map of the system has been published or if all the original system is currently in use.
The TBs I noted were all ZiU 9 (export model was ZiU 682) built at Engels and standard USSR fare of which around 2,000 a year were built from 1972 until the collapse of the USSR . ZiU stands for Zavod imeni Uritskogo. They have reinvented themselves as Trolza http://www.trolza.ru/ .
We think around 255 were delivered new to UB and on my visit the lowest number I saw was 30 and the highest 177. Some will have been written off in accidents and for canabalised for spare parts. The 4 in front of the fleet number may refer to the depot number which would be standard Soviet practice. The Soviet practice was also to send TBs to central factories for overhaul and they often returned in a different paint schemes with other modifications depending on availability of parts and colour of the paint available this week.
Some of these plants have also tried to build replicas!. Soviet steel was always prone to rust and major rebuilds were fairly common. I have been in such a workshop in Kaliningrad and when they take the panels off it a bit rough underneath! I brief history of the ZiU 9 is at http://en.wikipedia.org/wiki/ZiU-9 "
