Quote from FE Hoppy:
"We have a policy of no tankering if the landing runway is expected to be contaminated or if icing conditions are forecast for the approach. So regardless of length wouldn't do it."
Yes, IIRC that was the policy in my last airline, and may apply to most.
Unless I'm misunderstanding the OP, we are having a generic, academic discussion here for a student; neither airline-specific nor type-specific. The runway at the first destination (suggested to be Munich by the OP) may or may not be contaminated. But I think Piltdown Man and I agree that, speaking generally, contamination of runways is more likely to affect operations when the temperature is just below zero than at -15C. And, although one must always be super-vigilant, the same applies to airframes.