Currently Being ModeratedNov 8, 2012 10:45 AM (in response to bvoisin)
I don't know how to add the square bracket to the list of format options, but I can tell you how to change the end result to your liking, if you have the patience for it. You can use the Pages option for normal parentheses and export the result to RTF. Open the RTF file in TextEdit (or similar) and use Find and Replace to change the parentheses to brackets. Then Copy the list and Paste and Match Style to an area of the TextEdit document not formatted as a list. Then, copy this non-list that looks like a list back into Pages. When I did this there were a few spurious Tab Characters in the result that were easy to remove.
My personal leaning would be to do the list manually from the beginning.