i've never seen a clamshell on a Truss Arm either...doesn't look half bad either though i prefer them on guy wire arms or Bottom braced upsweeps...also Ornate S-Curved Arms.
i checked on street view. sadly this OV20 is no more, replaced around the summer of 2011. westbound I-30 has an image date of june 2011 and it shows the OV-20 across the freeway. eastbound I-30 where this OV-20 was has an image date of august 2011, with a new GE M-400R3 drop lens.