I have seen and serviced these types of systems. The system is essentially a VAV system. The diffusers in the floor have MOD's and are controlled by a zone stat. I don't deal with costs at all but I believe the flooring system is quite expensive. The raised floor tiles are sealed around the edges to prevent any leakage and the under floor base is insulated and sealed to prevent condensate on the lower level. I also remember humidity sensors to insure dry supply air. Computer rooms have been using raised floor systems for years but your application is a little different. The commuter room is usually one zone and any tile leakage will leak into that space so over cooling is not an issue. In an office environment leakage around the tile will cause over cooling in the space. I have to believe the tiles are very expensive. The one's I have seen are carpeted and probably made to order. The zone dampers are built into the tile. The systems that I have worked with were York which is now Johnson Controls. The system is very flexible, tiles can be moved to accommodate changes in layout. Hope this helps.
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