Perhaps it's more readable and easier to understand if the order of the clauses are swapped?
Children under 12 years of age will NOT be carried on Bus Eireann or Expressway services, where the following conditions apply:
- If the journey intended is greater than 30km
except when they are accompanied by a responsible person aged 16 years or over.
- If the journey intended is after 7pm.
BE's problem is that they can't prohibit the carrying of children to and from primary school.
But the wording they have chosen on that link, doesn't prohibit other scenarios that would be questionable eg. Mammy can put her 8 year old on the 10:00 from Cork and Granny can meet him/her in Busaras at 13:45.
Out of curiosity, I checked if I could buy a child ticket without an adult ticket from their website and I was able to get to Checkout. The Ts&Cs they have on that page are different to what's in the OP, and make a lot more sense.
Children under 12 years of age will NOT be carried, except when they are accompanied by a responsible person aged 16 years or over, on the following categories of Bus Éireann services:
All Expressway services - as detailed in Expressway section of Bus Éireann website Buseireann.ie or in the Expressway section of Bus Éireann’s published Timetable Booklet.
Non-Expressway services where the intended journey of the child passenger exceeds 50 kilometres.
Where doubt exists as to the eligibility of a child for unaccompanied travel, it is the responsibility of the passenger claiming such eligibility to produce evidence of age.