I could be mistaken, but I think its a 4th tier league game.
Both clubs have had "issues" shall we say. Rapid were disolved for financial troubles and two teams were formed in their place start in the 4th tier. I think a third club has now been formed by former players and thats the one the supporters have got behind.
There is a team (who City played) called FC FCSB in the top tier which lost the rights to the Steaua trademarks etc. FCSB is not an abbrieviation - thats the actual legal name of the club. The supporters don't like the owner, so I think some Steua fans have formed a new club in the fourth tier and I'm guessing they are due to play each other, but not much news from the Romanian 4th tier gets reported outside of Romania.
There is a similar story in Bulgaria regarding CSKA Sofia which is even more contentious. Copa90 on youtube have a couple of decent documentaries on both Steaua and CSKA Sofia if you're interested.