Just like the Fair Housing Act Design Guidelines, the ANSI Standards also requires 40" at the face of the base cabinet, counters or applicances at a pass through kitchen.
804.2.1 Pass-through Kitchens. In pass-through kitchens where counters, appliances or cabinets are on two opposing sides, or where counters, appliances or cabinets are opposite a parallel wall, clearance
between all opposing base cabinets, counter tops, appliances, or walls within kitchen work areas shall be 40 inches (1015 mm) minimum. Pass through kitchens shall have two entries.
There are two differences between the FHA and ANSI:
a) The clearance is not just between counters, but also between walls and counters. Below the 2009 ANSI A117.1 figures
b) The second difference is that the ANSI does not stipulate that the clearance should not be measured from the face of the hardware.
The requirements for the U-Shape kitchen is only for 60" between counters. There is no exception for a narrower or wider kitchen. Below the 2009 ANSI A117.1 Standard figure.