This is an interesting idea, I believe that initially it was thought that bubble CPAP might deliver some high frequency pressure oscillations to the lungs, as the bubbling in the circuit causes some small amplitude variations in the pressure in the circuit. I think that has probably been debunked, there is likely no significant CO2 removal as a result of these small oscillations in pressure.
On the other hand if you hitch up your CPAP prongs to a real high frequency ventilator then you might be able to deliver some non-invasive high-frequency ventilation, at least while the airways are open.
This group of researchers (Mukerji A, Singh B, Helou SE, Fusch C, Dunn M, Belik J, et al. Use of Noninvasive High-Frequency Ventilation in the Neonatal Intensive Care Unit: A Retrospective Review. American journal of perinatology. 2014) report a retrospective group of babies who were treated with this kind of intervention. During high frequency non-invasive ventilation there was a reduction in apneas, in oxygen requirements and in CO2. Of course the question is what would happen to a similar group of babies treated with standard non-invasive techniques.
The only way to know is by doing an RCT, which I hope is being done.