To answer the question, of course the same type of maintenance is being performed today! The priciples of steam locomotive maintenance haven't changed since this movie was shot, although techniques probably vary from engine to engine, and crew to crew (I do find the apparent British disdain for work gloves interesting). We have different tools today as well--although I do like some of the Brittish ideas, like that "flute" nozzle.
Last weekend, I was "lucky" enough to get the job of scrubbing out the firebox on our small oil burner in NC, just as was seen (but I had gloves on). Today, we hammer tested the stay bolts, also exactly as was shown (although we had a couple representatives of the Federal Government monitoring the procedures--we were undergoing our annual FRA inspection).
I guess for us, the difference is that it takes us many days to do the maintenance shown in the video (we're volunteers), whereas back then, it all took just a few hours. It's neat to see the turnaround time on that kind of work.