They work some of the longest hours in Europe, and so possibly in the world ... though the presenteeism culture means they're not actually "working" all the time. But having to be there, all those hours, is in part because of the assumption that they will be taking a siesta ... and many don't any more. I would say that most don't any more, at least not in the bigger businesses.
And so even if Rajoy is successful I doubt it'll have much effect. I suspect that small businesses will still close when they feel like it anyway!
For me, the more interesting part of what he's talking about is the proposal to bring Spanish time into line with GMT, rather than staying out of sync in order to be in line with Nazi Germany, which hasn't been around for, like, 70 years or so ...
For us in the Canaries, therefore, where shops often already close when they feel like it, and where we're already in line with GMT, I don't see much chance of much change ... and this all assumes that Rajoy is going to be in any position at all to pass any sort of legislation ...