I would doubt very much that transmission on ibus is affected by temperature. It seems to survive very low voltages, so I do not see why it should not work at low temperatures.
Ibus is quite short messages with both parity and a simple crc, so as long as the devices test on that I think missinterpretation is a lot less likely than message drop.
Having said that I am not sure what spec the chips are in automotiv in general. The Melexis TH3122 that is the ibus driver used by Resler is specified from -40...