While attempting to disarm the bomb on the tram, the ATF agent says to measure the current through a transistor. A multimeter is used, and the measurement was stated to be "40 ohms". Current can be measured by a simple multimeter only by connecting it in series with the circuit to be measured, which was not done. Furthermore, current is measured in amps. Ohms is a measure of resistance, a reading which cannot be made on an energized circuit.
The tram employee holds up a bundle of wires, saying that he (the bomber) cut the main cable and only he has control of the tram movement. This tram is moved by a motorized cable spool at one end. The tram can be stopped by disconnecting the power to the spool motor.