An R as a fleet car? You mean for someone to have as a company car?
Only if you have stupid money to burn. You will get crucified on your P11D for that amount of CO2!
GTD is quite a common company car and obviously comparable to the R as from same stable.
GTD to R
£4 k approx more for R over GTD
C02 is 127 for GTD and 159 for the R which is quite remarkable for the R (if believe it

) given a 1.6 Astra GTC is in 155 region (if memory serves me from colleague who selected one) as are 2.0 Ford Focus and Mondeo which are all seen as 'good' company cars - So all fall in the 28% BIK and all push £27-30 k in value
BMW are pretty good on the C02
Think the GTI is only just a smudge lower on C02
But the R is more comparable than think with other makes, and particularly those which you would consider company drives but are quite a way behind the VW, Audi and BMW on emissions.
Obviously you can go super green and cheap on company car, but if want a decent experience the GTD is a good compromise for a company driver but the R is not really a chasm apart and when compared to the Fords and Vauxhall where BIK is directly comparable and P11D value is not as far apart as expect, then R is also not the leap that think would be for what getting.
Of course economy is another thing, but if doing long runs even that's far more decent than expect or should be