I believe that it is possible to build a profitable ad-funded MVNO. It is also possible for MNOs themselves to introduce ad-funded voice and data tariffs. You don’t necessarily need to build a new MVNO brand like Blyk to maximise Ad ARPU.
Since the actual values in Blyk’s business plan and the wholesale prices negotiated with the Host MNO Orange in the UK are secret, Hess uses his own assumptions for the parameters driving revenues, costs and profit in the whitepaper's calculation. The outcome is a very educated guess work which probably hits the spot and helps to understand the ad based MVNO business model.