Taken from the 2002 NEC Handbook.
210.52 Dwelling Unit Receptacle Outlets.
This section provides requirements for 125-volt, 15- and 20-ampere receptacle outlets. Receptacle outlets required by this section shall be in addition to any receptacle that is part of a luminaire (lighting fixture) or appliance, located within cabinets or cupboards, or located more than 1.7 m (51/2 ft) above the floor.
Permanently installed electric baseboard heaters equipped with factory-installed receptacle outlets or outlets provided as a separate assembly by the manufacturer shall be permitted as the required outlet or outlets for the wall space utilized by such permanently installed heaters. Such receptacle outlets shall not be connected to the heater circuits.
(D) Bathrooms. In dwelling units, at least one wall receptacle outlet shall be installed in bathrooms within 900 mm (3 ft) of the outside edge of each basin. The receptacle outlet shall be located on a wall or partition that is adjacent to the basin or basin countertop.
Handbook Commentary
"Section 210.52(D) requires one wall receptacle in each bathroom of a dwelling unit to be installed adjacent (within 36 in.) to the washbasin. This receptacle is required in addition to any receptacle that may be part of any luminaire or medicine cabinet. If there is more than one washbasin, a receptacle outlet is required adjacent to each basin location. If the basins are in close proximity, one receptacle outlet installed between the two basins might satisfy this requirement."
That may be what your GC would prefer but the NEC does not require it and if he didn't spec two one is all he gets.
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Tom