Equal Spacing Spread Command

 Yes if you have the Allegro PCB Designer with High Speed Option (or Allegro PCB XL) license level. Look at Route - Resize/Respace - Spread between Voids. There's a video on Youtube:- https://www.youtube.com/watch?v=hU20ZvAddx8

If you don't have this license you could try increasing your line-line spacing rules in Constraint Manager then use the Slide command, pick a cline at the bottom of the area and slide (Route - Slide) with the Option set to Shove Preferred the clines should jump apart to the new spacing rules. You will propbably have some tidying to do but it's one way... 

Has anything changed in the last few years? With a large number of cline segs running parallel to each other, is there a way to distribute traces between and outer set of cline segs? The feature below has a similar functionality but doesn't allow the width of the "channel" to be specified by selecting the outer set of cline segs.

One example where this is important would be to reduce crosstalk amongst traces. I may route a board and, when I'm done, realize there is more space available than I thought. Physical separation between traces is important, so I'd like to spread out the traces and consume all the board area to separate the traces. In this case, I could slide one cline seg and then spread out all segs between the outer pair. Has this capability been added since this post was created, or is there another way?

So... nothing? Has this feature been requested of Cadence? It seems like most of the logic is in place, but the edges of the "lane" should be defined by traces instead of voids.

I just plop down 2 temporary vias to define the channel (with drcs, doesnt matter), spread,  then delete the vias.