don't quite follow the logic there - if Doncaster and other airports are dropping Alicante flights, what has Humberside got to offer them?
Quite simple, a fairly large catchment area in which, as you say, other airports cannot sustain (rather than dropping) Alicante flights, but HUY can.
If you live within 60 miles of HUY and want to go to Alicante with no alterantive but EMA, DSA or LBA, its a no brainer that you fly from HUY if the price is right.
I rather suspect that HUY Management will have had to agree to some fairly stringent commercial terms to ensure that Ryanair come back, but it gives the customer the choice to fly from there, which, in my experience means the same customers will seriously consider using their local airport next time around.