"There's a brief view of a 1920s vintage bus in the station yard when Collins returns to Ireland after his release from prison in England.
Also,there are various shots of pseudo-trams,which in fact run on rubber tyres,in the scenes set in Dublin,which I think were filmed on a huge custom-built set.
However,the type of tram depicted wasn't brought into service in Dublin until after Collins' death!
In one scene,a "tram" passes behind Collins and his companions which doesn't even have its trolley pole on the wire! I didn't know the Dublin United Tramways had conduit lines at this
time!" (thanks Alan Sinclair)
The Internet Movie Database reports a 1980s-vintage bus appearing in the background of one scene, but having seen the movie I'm wondering if this is one of the trams.