Amelia, I'd take each and every story in the Derry News with a huge portion of rock salt. I'm sure if you asked the same people who operates what routes from LDY they wouldn't know.
The recognised (average/ball park) figure for an airport to break even is 1million pax. This of course doesn't take into account operators like Ryanair, so perhaps LDY would need more than this.
A similar(ish) example of a council run airport being privatised is Exeter. Privatisation there has done good things for the airport, and the council has been able to channel some of the funds generated into developments elsewhere in the city. The difference being, Exeter residents ALL pay council tax, whereas in Derry rates are paid (mainly) by homeowners. So, naturally council income will be very different.