A dispute over the value of a key parcel of railyards land is getting closer to a resolution. An arbitration hearing began Monday over land likely to become the home of a future arena and a regional transit center. On Monday, two weeks of witness testimony began to help determine how much the city of Sacramento should pay developer Thomas Enterprises for nearly 33 acres of prime land adjacent to downtown. The land also holds historic value as the western start of the first transcontinental railroad. The city already paid $55 million for the parcel in 2006 after Thomas Enterprises bought the 244-acre former railyards site. But the city and the developer have never agreed on the parcel's