That link you provided seems to state clearly enough that it's illegal.
A public place is usually defined as a 'place to which the public have access', and so it includes car parks, apartment blocks etc. This also goes for road traffic offences,, like driving drunk or without insurance. Gated communities would be different but these aren't too common in Ireland, although there are a few.
It seems that companies leaving leaflets on car windscreens could be easily prosecuted. It may also be the case that the property owners could also be prosecuted.