For example, whenever there's a major news story they see traffic spikes that would make you weep.

Internally on the other hand, where the stakes aren't so high, they make heavy use of rails, node, go and all that cool stuff. They know what they're doing.

Check out this list of some of their machines, from part of their monitoring system which is for some reason left open: http://support.bbc.co.uk/support/rrd

Here's is some data about their peering: http://support.bbc.co.uk/support/peering/

Yeah that's right. Peering.

EDIT: you're right that they could probably implement this quite easily, but the point is they can't just throw up an agile solution at the scale of the BBC, even if it seems safe.