The following case has been getting a bit of attention in the media lately, thought it was worth sharing.
City of Brampton v Robinson 2017 ONCJ
Short version is that a motorist made a three point turn where u-turns are prohibited (he pulled into a driveway, backed out then went the opposite direction). At trial he argued that he never made a u-turn since that would be one continuous motion. He was convicted. While this is a non-binding decision, it's worth noting the Court's logic, which even traffic lawyers seem to agree with. Basically the HTA states that it's illegal to "proceed in the opposite direction" and that a u-turn does not need to be a continuous motion. The signs are there to prevent people from turning around, even if they try to be creative about it.