Can I run data cables in the same cabinet as a service panel?
In the same decorative wooden cabinet, yes. 

In the same conduit, raceway, gutter or service panel, no, unless the entire low voltage circuit, and the involved appliances, are all built to mains wiring standard... 

So for instance the Ethernet cable could not run in a power conduit, come out to an RJ14, and go to a computer in the normal way with a commodity ethernet cable, since neither the RJ14 jack nor cable is rated for mains power.

The problem they are concerned with is any random wires in the raceway shorting together, so suddenly there's 240V on your ethernet cable.