The front-end URLs are:

Synchronous front https://serveis3.nt.aoc.cat/siri-proxy/services/Sincron
Asynchronous front-end https://serveis3.nt.aoc.cat/siri-proxy/services/Asyncron
Asynchronous front-end-response https://serveis3.nt.aoc.cat/siri-proxy/services/AsincronResposta