I think your point is possibly right – seeing access to Heathrow as crucial could just be a legacy of old ways of thinking. And certainly I’ve no problem in principle with the sale of Aer Lingus.
But I think we do need to be clear that selling Aer Lingus means it will be a fully commercial operation. Golden shares will not enable the State to maintain any meaningful control – which may not necessarily be a bad thing. However, we do need to be clear that if their new owners decide Heathrow – Dubai is a more profitable route than Heathrow – Dublin, then that’s what they’ll do.
This is true, however are there any controls currently in place to ensure that they do provide a service between London and Dublin? Or do they have the authority to drop this route in their current format?
There will be a profit to be made on Ireland-Heathrow well into the future (BMI use LHR slots to serve DUB without being forced to) so I don't think it should be forced on Aer Lingus by way of law. It could end up being another farce like the Shannon stopover where business and common sense are cast aside for local political considerations.
Aer Lingus are not statutorily obliged to serve LHR (as Cork found out, the only place they have to serve is Shannon, and then only if they want to keep flying to the US)
Furthermore, when EI becomes a public company the company's obligation is primarily to shareholders unless legislation (like the Air Canada Public Participation Act) forces obligations on them. The Minister can instruct his Board appointees to oppose any move to drop LHR but I don't think that is currently the case.
Therefore, to answer your question - Aer Lingus could drop LHR and sell their slots at any time. However, they are codesharing with BA and would have to deal with ending that arrangement also. I don't think they would do so in a million years btw, it's SIPTU scaremongering - the only guy who would have done it is WW and he's gone and taken his O'Leary aping fantasy to BA.
Dublin-London is still one of the heaviest air traffic markets in Europe with significant business content, so there is money to be made for the moment, especially with A321s and A320s being the sole equipment (no 146s from time to time) and making good use of the slots.