So now you're in the mechanical department Dutch?
The units NS59 is working on (there are only two in the area and I presume we're talking about the same ones) will be running on Class 2 track, max 30 MPH for passenger. It's not like they will be bringing a train down from 79 MPH and I doubt heat will be an issue.
Furthermore, the result could actually be the opposite. At comparatively SLOW speeds the composition shoes have LESS effectiveness - they have to be warmed up before they grab well and on a few occasions when going from a railroad with cast iron shoes to one with comp shoes, there was an adjustment in my thinking needed to compensate for the longer stopping room required on a winter day with comp shoes. Maybe the newest ones are better. And I think you'll find comp shoes are far more common than you think Dutch - maybe your line still uses cast iron but I'm betting that within the next 5-10 years the cast iron shoe becomes a rarity.
My opinion is don't sweat the heat thing - it won't be an issue.