I think the statement 'Good for them at the time ' is actually a very telling statement, as it suggests to me that it is indeed a flexible thing-probably tied to tech level, civics choices and certain improvements and wonders. My theory, for what its worth, is that it will be based around the idea of distance and OCN, but that both of these factors will be more flexible-within each game-than in previous iterations, if that makes sense.
As for collateral damage, we know from another interview that this is related to the particular siege unit. i.e. each catapult will probably only be able to damage 1 additional unit, wheras radar artillery will probably be capable of damaging the full 6 units. In this regard its not much different from the bombardment strength system of Civ3-though it may or may not be as variable (for instance, as I asked above, I am curious as to whether a radar artillery can hit from 1-6 extra units, or will it always be 6?) Also, the amount of damage a unit of a particular strength does sounds like it will also be variable-given the statement that a tank may need one or 2 hits to finish off a spearman. Again, just speculation on my part.
Yours,
Aussie_Lurker.