The Engagement Control Roll would be made against each of the hostile units the enemy player wishes to have interrupt your progress through the Sector or Zone. The rule on pg167 pertains to ground units, where there are a limited amount of Formations to deal with when crossing, but little on ACS where there can be no stacking limit on Engagements on the CRM. Engagements on the Capital Radar Map must use Engagement Maps (see pg.186) within each Sector, and so you still have the ability to completely bi-pass a hostile if you have the speed for it. On pg.176 you have this:
"Multiple Engagements: Because an aerospace zone can hold
multiple Squadrons, it is possible to have multiple engagements and
a single Squadron engaged with more than one opposing Squadron.
Once a Squadron is engaged with another Squadron, it may not
declare an attack on another Squadron. However, it may be engaged
by another Squadron that has not already made an attack"
So, if, say, you DID have multiple hostiles intervening a Zone you intend to pass, I recommend you use the Evasion and add +3 to your Engagement Control Rolls since you have a high chance of being interrupted by one of these hostiles, all of which would have a chance to roll against your units to intercept if they are determined to cross this hostile zone. The only thing the rules do not have is an alternate way for units on the Abstract maps to functionally resolve Engagement Control Rolls effectively. As Overruns, for example, tell you to use the size of the units as a modifier. Always use the Tactical Values for Aero instead, as it makes far more sense.