It's Ekka time, the time of year when people who are too lazy to walk 5 minutes from Bowen Hills or Fortitude Valley stations, pay extra to take a train around the Exhibition Loop to Exhibition Station. It's also the time of year that train fanatics ask themselves why the Exhibition Loop and Exhibition Station cannot be used by passenger trains year round.
There is good reason why running year round train services around the Ekka Loop does not make sense. Without making conflicting moves (i.e. trains crossing the paths of other train services) trains can only run in an anti-clockwise direction around the loop, as per the special Ekka train service. Running services from Ipswich or Caboolture to Brisbane and reversing via the loop (e.g. Ipswich to Ipswich via Ekka Loop) is technically possible, but would add conflicting moves where trains enter and exit the loop. These conflicting moves would reduce network reliability and capacity compared to the current service patterns. Running services from other lines via the loop would add even more conflicting moves to the system as they have to cross the Ipswich/Caboolture Line.
What about services that currently start or terminate at Roma Street and run via the loop to/from Mayne yards? Could these stop at Exhibition? There would be reasonably frequent services to Exhibition during parts of the peak periods, but at other times services would be somewhat sporadic unless changes are made to the line pairings or service patterns. There would also be considerable costs to rebuild Exhibition station to allow sufficient access to Bowen Bridge Rd. Given that the nearby RBWH and RCH are now served by the Inner Northern Busway, would this really be cost effective?
However, it's not all bad. The much needed Cross River Rail is currently expected to surface near Victoria Park, and run along the Exhibition Line alignment to join the existing rail lines north of Bowen Hills. Extra tracks, and a grade-separated junction around Mayne would be required to allow for sufficient track capacity. A rebuilt Exhibition station would then almost definitely become a year round station, serving the redeveloped RNA showgrounds. It may also allow for the elimination of the special Exhibition Loop services, allowing for more capacity on the main tracks (currently used by Ipswich/Caboolture Line) through the CBD, and extra capacity on the Exhibition Line for freight services bypassing the CBD. Surely a win-win situation!