I'll have to look at it a bit later, tired atm and times stretched as is for my workload.
Displacements would be what your looking for, I still have an older tutorial covering the basics of it online: Displacements - Blend - Sewing and minor Subdiv. The new tutorial will not be completed for some time on that as its covering literally everything to do with displacements. Slowly I'm finishing off the draft on my profile though.
Subdivision is what your interested in. The PDF link deals with tunnels directly. To create the cell effect with those displacements you would need to make another inverted tube so to speak subdivided the same way the tunnels are. Just be sure to check off the all the option boxes for the black displacements so that players will pass through it fine without gimping out servers.
Make a 64x64x64 box, turn the whole thing into a displacement, click subdivide.
Then with 6 separate boxes make an outer shell around it like you do a normal crate etc. Select the 6 inside faces - all edges should be touching - and turn them into displacements only and subdivide. Do the same option check as the tunnels thing I mentioned to remove errors.
That would require a whole new mod just because of the scoring system it would need, couldn't quite make a map with all that contained, tried something similar where I reversed the team models to have CT's planting demo charges and T's defending. Scoreboard file cannot be edited via the map.