Hi,
The dimensions of the shield and the location of the main I/O headers matches those of the Arduino shields otherwise the Arduino shields would not fit the AMICUS (mechanically....electrically they might not anyway as we've seen).

.brd files are board files for Cadsoft EAGLE layout, you can download the free version of EAGLE from their website and use it to extract any dimensions you need - if you don't want to use to create/edit the shield files.

(Hoefully Lester jumps in and corrects my if I make a mistake here).
The AMICUS18 can be used with both 3.3V and 5V devices, it comes with the 18F25K20 which is a 3.3V device and therefor it is set up for 3.3V. The board is powered either from USB or extaranlly by ~9VDC and it supplies 5V and 3.3V to the shield. There are solder-pads available on the board which, when bridged feeds 5V to the PIC instead of 3.3V in which case the I/O's are obviously 5V instead of 3.3V.

There is a schematic on page 11 in the hardware manual.

HTH
/Henrik.