Evidently a technique sometimes used for ice racing is 'tractionizing', where a machine chews up the top layer of the tire. Otherwise winter tires these days seem to often use lots of siping.
The unidirectional tires with the v shaped grooves seem to get by with less siping for rain and such, but shoulder lugs, adequate voiding/grooving, and siping seem standard on a typical all season, M&S, or A/T tire, voiding increasing repectively. Mud & rock tires go with lots of voiding and minimal siping, they do well in fresh snow, and then they seem to populate ditches when the ice forms. High perfomance tires with large tread, minimal grooving and siping seem to populate ditches when it rains.
Siping was popular around here for awhile for rain and especially winter conditions, but it seems that makers are providing tires with more siping, or are at least offering more models where some do have more siping.