They were developed about 3 years ago by a civilian engineering company, and are currently being trialled on the A1065, between the A11 and the A47 in Suffolk/Norfolk - and posssibly elsewhere.
We are also trialling a similar reflective stud, which retains the light but doesn't have the sparkle effect, with a long term view of installing them on subsidary taxiways - this will then mean we don't have to install taxiway edge lights with the associated running and maintenance costs.
Up to now they've done a very good job, and we've had very favourable comments.