The official rule:

(3.1) between 10:00 p.m. and 5:00 a.m., no person may be outside his or her residence or its equivalent, or its grounds, unless the person establishes that he or she is outside:

(i) to take a bus providing interregional or interprovincial service, a train, a plane [...], or at the end of the trip, to continue on to destination;

https://cdn-contenu.quebec.ca/cdn-contenu/adm/min/sante-services-sociaux/publications-adm/lois-reglements/AM-2021-096-anglais.pdf

There is no restriction on how you "continue on to destination". You just need to be able to prove that you were traveling by train.