Interestingly, there was a Man-Dub flight today that operated under a 4 digit 'EIR' flight number even though it was operated by a mainline A320.
It wasn't under EIR number, it was an extra scheduled flight which was EI2xxx, EI use 2xxx for any extra scheduled flights. EIR is 3xxx.
The reduction in services is demand lead. Jan and Feb are very quiet months for airlines.