I don't know if it is still the case, but earlier after the merger, there were instances of EWR/IAH flights coming in at Term. 1 because of redeployment of aircraft--clearly one-off circumstances. The rule of thumb noted in the previous posts is about as accurate as you'd get from UA. If someone is meeting you, his could be a major headache.

good travels,

Flyer 420
in Seattle

Sorry, read the op too rapidly, I have heard of no departures not following the Ter, 1 IAD/ORD/SFO/LAX Term 5 IAH/EWR rule.