They’re going to get banned for drink driving so that person would be an ex-driver. 
However, the nominated TM is legally obliged to report the drink driving offence to the TC as the driver was at the time of the offence employed by the company who held the O-licence. The TC will want to know how the incident was handled.
So, it does affect the O-licence, but if handled correctly, the O-licence holder need not be excessively penalized. However, I’d expect them to be told they need to implement some kind of policy to make sure this doesn’t happen during work times, because if someone is driving their car and claiming they didn’t know how long alcohol stays in your system, then what’s to stop them driving their truck with excess alcohol in their system? That’s how the TC will think.
So if this guy’s former workmates find in the future they’re subjected to random breath testing, then they know who’s to blame.
Getting points on your licence, eg speeding - in your own car on your own time - also has to be reported to the TC.