Abstract: Apparatus for laying underground cable or conduit (such as innerduct) includes a vertical cable plow connected to the boom of an excavator, the excavator being mounted on a first flat-bed rail car, and a second flat-bed rail car following the first for carrying supply reels of cable or conduit fed from the second car to the first. Cable guides guide the cable or conduit from the supply reels to the plowshare and through the plow assembly to the desired subterranean level in a ditch made by the plow. The first and second flat-bed cars are preferably pulled by a pair of conventional diesel-electric locomotives. A rigid element mountable to the first flat-bed rail car and extending outward from either side of the first flat-bed rail car transfers torque on the plowing assembly to the rail car. The rigid element (“boot”) is preferably removable to temporarily narrow the apparatus for travel mode. The apparatus may be installed on a flat-bed truck or a canal barge instead of a rail car.