Its about avoiding mid-airs
The point of the thread is not how easy it is to navigate the lane, but whether or not a mid-air is more likely in it. Whenever you concentrate aircraft by defining a track you do make it easier to know where to look to spot the other aircraft (assuming they are following the published procedures), but you also put aircraft closer together more often than random manoeuvering and therefore create an organisational level risk - the first layer of swiss cheese if you get my drift.
If you think back to your aviation medicine training, one issue to remember is that meeting an aircraft head on or overtaking at the same altitude, such as in a lane, is the hardest way to spot conflicting aircraft, especially with an urban background. In this situation the aircraft cross section is the smallest it can be, and the 'ballooning rush' as you get really close is the biggest amount of relative movement. By then it can be too late. The training area on the other hand with its more random tracking creates more relative velocity and crossing movement, with bigger cross sections, which attracts your attention earlier.
So the question is: Is everybody in the lane maintaining a excellent lookout to minimise (but not eliminate)the risk? Well if they are having to look at maps and compasses or heaven forbid the GPS set to navigate the lane, I would suggest not. So can a radio call help? Yes. Directed lookout is more effective and therefore safer than lookout on its own. You still need to look out though as a matter of course and not just rely on the calls. Isn't that what radar advisory services for VFR traffic are about?
What is the real problem here: Is it the people making the radio call (ie self provided directed lookout) or is it the overcrowding of a radio frequency? It would be safer and do more to avoid mid-airs to provide another frequency than to outlaw the calls.
Regards.