Any source you use as background must be compatible with OSM. Many imagery layers which may be more up-to-date usually have restrictions as to their use.
I’ve had a look at the site: I presume WMS is licenced CC-BY 3.0. This is not directly compatible with OSM, but if the authorities write that they are willing for it to be used for OSM then this can be arranged, and it can become a layer offered by editors.
I would suggest perhaps asking on the talk-es list if anyone has direct knowledge of dealing with Regional governments (IIRC imagery from Castilla y Leon was made available this way quite a number of years ago (I have relatives from around Palencia)