Our company signed up to it perhaps 18 months ago. Quite a few folks have bought bikes through the scheme. Nearly all of them were existing cyclists though and I'd have said there was perhaps only person who cycles to work reasonably regularily who didn't do so before the scheme was introduced. Even they were prompted to start cycling by an office move, not by the scheme.
Nearly everyone else who's bought bikes under the scheme either hasn't continued to cycle to work over the longer term or was already doing so. In the case of the latter folks then only a couple actually bought the bikes they'd then use to commute on. The rest either already had ratbikes for commuting on and continued to use them, with the scheme bikes being their "best" road bikes, or else bought mountain bikes.
We've also had one person who's now bought two bikes under the scheme. The first one they do use to commute on, the 2nd was a mountain bike.
So I'd have to say our experience is that, despite perhaps 15 people buying bikes under the scheme, I can't think of one case where it's introduced someone new to cycling to work and it's then stuck.