Just as a little fly on the wall here, that fly has seen a few things that, if seen through new eyes, may bring a better understanding to all involved.
1) The thread originator has stated that there is interest, a desire to bring a dog into the cathedral and is asking for information to know what is accepted.
2) Some contributors advise that it is not.
3) Another tells of her personal perspective.
Perhaps something that needs to be offered is regarding a point of respect. As we travel to different countries, we experience different customs and ways of doing things, different foods, clothes, belief systems.
When walking the Camino, for most of us, we are in a different country, guests of that country. In fact, we are also a guest of the Roman Catholic Church, while on the Camino. It is the Church that created it. They are our Host. Should we not act appropriately, and if there is something that we wsh to do, for ourselves, that goes against the local custom, perhaps ask permission before doing it?
Personally, I am not a dog owner, at the moment, but love all dogs. In my Church, dogs are welcome, but our society, where I live, is much different from the Camino, definitely a different Country. But dog owners have always asked permission to bring their dog into pur church.
The act of asking is a simple courtesy to the Host.