No idea what that company might be, but I'd imagine they don't use bikes just for the "bus factor" risk of that person getting into an accident and the envelope lost.
Then you have the main security cordon, a quad / box. They would be on motorbikes, but it would be like guards, and since the traffic is already cleared by the forward section, it would just go at the fastest speed the cyclist courier can go.
The cyclist is in the middle of the quad/box.
Then at the back you have a rear section (also 3 NYPD off duty cops on motorbikes with firearms licenses and authorized to shoot with no consequence because they are union protected), which will block traffic from coming too close to the courier.
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