My '07 TCH's engine rev's higher on steep inclines than my '07 XLE-V6.
So did my '04 Prius. The TCH rev's less than the Prius but it still revs on inclines.
I tend to disengage the cruise control on the TCH in hilly areas and manage the conservation of momentum by foot. eg. accelerate on down hills and slow up a bit on upslopes if it's doesn't cause problems with other traffic.
Be advised, if you end up on an upslope that the ICE can not negotiate on it's own (without battery assist) you could find yourself in a bit of a bind if the traction battery becomes depleted. This situation might be rare but could happen. Just be advised.
I've also noticed that at slow speeds (<15 mph) I can negotiate very steep >20% inclines on battery power alone. Kind of an interesting experience.