The ITRS value accounts not only for a single area-to-area cap/length but for a full-around-the-wire cap/length value, this means Ctot/length = Cup/down + Cleft/right + Cfringe,corners -- and thus states a worst-worst case.
With metal_width = metal_pitch/2 and an appropriate value for metal_height = 150nm we can calculate:
Cup/down + Cleft/right = 2 * ε0εr * (70/290 + 150/70) = 1.22 pF/cm , which makes 61% of the ITRS value. The leftovers are easily covered by the fringe cap, which just can be estimated -- or calculated by a 2-dimensional field solver.
For the review of your question I got help from an Intel guy -- thanks a lot, Alfred!