kcockayne, Guernsey is not an EU member state and is thus not subjected to EU competition or state aid rules. But Article 345 of the Treaty on the Functioning of the EU (TFEU) specifically protects the right of member states to nationalise industries. Art 106 (often cited by those who claim that EU law bans nationalisation) doesn't ban it; it simply regulates how nationalised firms can behave with regard to competition (although the ECJ has recently been interpreting this rather more aggressively). Nationalised rail and electricity networks persist in Europe; so even if Guernsey's relationship with the EU was to change, Aurigny would probably be safe.
You say Aurigny was too slow to get on with the business of Tri replacement. But remember that the ancien régime, so to speak, saw no need for it. Mark Darby arrived in Sept 2013, and by Nov CS-TGG was on trial on ACI-SOU. With a shortage of adequate aircraft (both types and airframes), with 20 year old aircraft, with no manufacturer support (for the first two aircraft), with four days of sim training (in Germany, near Braunschweig) at a cool 25,000 EUR per pilot... I think you get the idea.