To the first part of your question, it is likely that some albergues and hostels will be open. Note, however, that they are fewer in number and frequency on the del Norte than on the Francese and, should the albergue in a pueblo be closed, the only alternative will be commercial accommodation or to travel on further-- on the Francese, there would likely be another one or two albergues. As well, currently there are firm travel restrictions between provinces ("autonomous communities") and, while that will likely have changed by April, nobody knows.
Posters' comments about crystal balls are not only jokes. We can't project into a rapidly-changing and very serious situation. A crystal ball will likely serve as well as anything.
I have no idea about train tickets and April tickets are unlikely for sale at this point. This (
https://www.seat61.com/) is a very well-maintained site.