THE ACFT COLLIDED WITH A POWER LINE 50 FT AGL WHILE MANEUVERING OVER A FREEWAY AT LOW ALT. A PALM SPRINGS ATC EMPLOYEE WHO WAS DRIVING HIS CAR IN THE EASTBOUND LANE OF I-10 APRX 10 NM EAST OF THE BANNING ARPT, OBSERVED THE ACCIDENT ACFT ON A WESTBOUND HEADING AT ABOUT 30 FT AGL. A FEW MOMENTS LATER THE SAME OBSERVER SAW THE SAME ACFT FLYING EASTBOUND AS IT FLEW OVER HIS CAR AT AN ESTIMATED ALT OF 30 TO 50 FT AGL. THE ACFT WAS IN A LEVEL FLT ATTITUDE AND APPARENTLY IN NO DIFFUCULTY. THE OBSERVER SAW THE ACFT COLLIDED WITH AN OVERHEAD WIRE AND PITCH DOWN. THE ACFT WAS RECOVERED FROM THE FREEWAY CENTER SECTION WITH A HIGH TENSION WIRE IMBEDDED IN THE LEADING EDGE OF BOTH MAIN LNDG GEAR STRUTS NEXT TO THE FUSELAGE. THE HEIGHT OF THE WIRES WAS MEASURED AS 50 FT AGL BY CHIPS (CA HWY PATROL OFFICERS). THE STUDENT PLT HAD BEEN INSTRUCTED TO PRACTICE TAKEOFF & LNDGS. THIS WAS DONE FOR ABOUT 1+ HRS AS THE CFI WATCHED. AFTER 2 HRS, THE ACFT LEFT THE ARPT AREA. 15 MINUTES LATER, THE CFI WAS INFORMED OF THE CRASH 8 MILES EAST OF THE ARPT.