Not seeing anything about breaking any speed record. The article just mentions going 50 mph, which doesn't seem like any sort of feat for a conventionally powered train.
The real importance would seem to be the demonstration of a realistic way to use zero-(CO2)emissions technology to run trains without having to string electrical wires over tracks or make new rail systems. Just change the locomotives to use hydrogen and oxygen in fuel cells, and they can use our existing infrastructure everywhere.
Short passenger trains are one thing - I wonder how this would work for moving freight. They would probably need hydrogen "tenders", but that seems totally feasible.
Of course, the real issue about making it "clean" is where the hydrogen comes from. It takes energy to make that "clean" fuel, and if that energy comes from "dirty" fuel, then there isn't any real improvement. As with electric automobiles, they are only really clean when the basic energy source used to charge their batteries is solar or wind (or maybe some folks include nuclear). If the basic energy source is coal, oil or natural gas, then you are really just changing from running your car by burning gasoline or diesel to effectively burning coal or oil or natural gas.
Britain does have a plan to use nuclear power to get to "zero [CO2] emissions", so this fuel cell technology does at least seem to make some sense for them. However, they really aren't progressing according to plan on their nuclear programs, with 3 of their 6 plants being decommissioned, and only one of the remaining 3 actually being upgraded according to plan. The public still just does not want nuclear power. But, running everything on wind and solar is not looking very practical when considering adding all these transportation energy uses to the demand, particularly automobiles, which will be usually recharged at night.
Toyota has now limited its manufacturing of electric battery powered cars because it is betting on hydrogen fuel cells beating out battery power in the medium term future. I think fuel cells for trains are a much better bet than fuel cells in automobiles.