This means that we cannot yet finalise the integration plans with VLM, and we cannot commit a VLM aircraft outside our core network at this point.
Seems a bit of a thin excuse. VLM have sent an aircraft over to Dublin many times on subcharters for Aer Arann and others over the years. They have plenty of charter/subcharter capacity; it's a significant part of what they do.
My guess is that the commercial terms for the PSO flights are now inappropriate for current fuel prices, but they don't want to admit it.