117,443 man hours isn't much on labour-intensive projects such as a tube-station refurb.
Taking a prudent example of a person working 8 hours a day for 45 weeks a year with no overtime, each person works 1,800 man hours per year.
Therefore, 65 workers would generate 117,000 man hours per year.
In other words, the project needn't have been going for years; they just have a lot of people working on the project.
In the construction industry, ROSPA encourages (indeed, I think it is a statutory requirement) construction companies to display accidents statistics in the way shown (ie. number of man hours per incident).
Construction projects are by their very nature extremely labour intensive. 65 person years is actually quite small for something like a tube station refit.
Add to this the health and safety aspect: the HSE enforce rules that prohibit anyone working in potentially dangerous environments to work alone, so a lot of casual labourers work alongside the more skilled team-mates.
Add to this the heavy demarkation of specialist 'trade' skills: welders, electricians, pipe-fitters, etc.
Just because you see limited evidence of progress doesn't mean to say there isn't a lot of work going on behind the scenes.