[douglas]

Anything that produces a log message happens in the same order as the log messages. Messages between players are processed first, then all orders are exected, then intel and research (not sure which of these two is first but they both produce logs so it's easy to check), then resource production, then maintenance expenses, then construction, then miscellaneous end-of-turn stuff like repairs, training, and value improvement plants.

Of the things you listed, they would occur in the following order:
Resource trades with others
Automated Ship Movement/Combat against Player
Intel against Player/Intel player conducts against others
Resources aquired
Ships Built/Facilities Built/Units Built

For the situation you outlined, player 3's attack would happen first.