Phone Trainer Evolutions

[ker-plop]

What determines when the Pokemon of phone trainers (guys who call you for rematches) evolve? I recall that Hiker Anthony (Route 33)'s Machoke sometimes becomes a Machamp... but I don't know how that happens. Does anyone know?

 

[~Bent~]

It's after a set number of battles. However, the number of fights changes is different with each trainer, and there's no collection on the internet of such fights...

 

[ker-plop]

Well, I'm trying to build up a chart of that, so I thought I'd ask. Just seems like the speed of the evolution differs each time I play through.