The trio - made up of two Dublin firms and London-based BPTW - had travelled to the city expecting to hear one winner announced.
But instead, the organisers announced that they could not pick one overall first choice and would instead split the Eu15,000 (£10,500) prize-fund three ways.
The local council is yet to reveal which of the proposed masterplans it wants to be taken forward for the site.
BPTW's Anna Parkinson, Justin Kelly and Ruairi Molloy were joined on the winning podium by Carew Kelly Architects and MCO Architects.
A spokesman for BPTW said: 'We certainly expected that there would be a winner announced when we went over there.
'But this is the kind of thing that might happen when it comes to designs,' she added. 'We were not disappointed'.
If BPTW's scheme is eventually chosen for the site, it would involve the construction of a dense mixed-use development on a site adjacent to the centre of the city.