Mine Clearing and lanes?

[Ubercat]

The manual, at the top of page 46, states

"As long as the Engineer or Mine clearing unit stays in the minefield, at the start of the next turn the unit is considered to have cleared lanes at that point and other units can safely enter the minefield in Travel mode without suffering a minefield attack."

This doesn't appear to work as described, because the last two times I did this, the T-mode unit suffered losses from the mines. I moved the mine clearing engineers in first, waited a turn until the mines had reduced a level and the word "Mines" was no longer in all-caps, and then moved a T-mode battalion in.

Does anyone have a more up to date explanation than the manual about how this works?