Complex sentence: Although the recent extension to Berezovaya Roshcha was significant as it would have finally allowed to end the shuttle regime, the station was opened with only one tunnel complete, the completion of the second one (early 2006) will allow for a standard regime to begin.
Split into simpler sentences: Although the recent extension to Berezovaya Roshcha was significant enough to end the shuttle regime on the line, the station was opened with only one tunnel complete. The completion of the second one (early 2006) will finally allow for a standard regime to begin.