As indicated in my reply to the Deputy's Parliamentary Question No. 508 of 22 May 2018, issues relating to the provision of infrastructure at train stations on the heavy rail network outside of the Greater Dublin Area and the cities - such as the matter of a bridge at Carlow train station - are an operational matter for Iarnród Éireann which receives Exchequer funding via the National Transport Authority (NTA).
I understand that following my referral of the Deputy's question, the NTA informed the Deputy in correspondence dated 24th May 2018 that with planning permission in place the NTA will fund the project and that it is expected that the footbridge will be completed by mid 2019.