The comments above stating that using explosives to destroy explosives 'blowing them apart' are incorrect. If you place one explosive hard up against another and detonate it it will explode as one.
If you place it CLOSE to another one it may depending on the power of the explosives and the distance. This is referred to as Sympathetic detonation - http://en.wikipedia.org/wiki/Sympathetic_detonation

Long story short - You should be able to detonate other explosives by putting your own near them as per the original ticket. In a game such as Arma the sympathetic detonation distance should be increased as it is too fiddly to attempt to place them directly or close enough to ensure sympathetic detonation (compared to the ease in real life)

More:
http://www.dtic.mil/dtic/tr/fulltext/u2/a197687.pdf (p 3)

This also happens in any place with a dock - eg. the docks to the east of the airfield. The unit is spawned with his feet on the ground. I assume this is part of the editor allowing a unit to spawn inside a building if it is placed on top. This is clear when you put a unit on the docks to the east of the runway - the unit will spawn inside the docks (hollow model?) and be unable to move outside them -- the terrain is visible and you can walk around a small area but are blocked by what I assume is the collider attached to the dock.

Summary - When placing a unit on a dock, the unit spawns on the terrain which puts them inside the dock object.

In addition to the above comment.....
The Alpha is missing a lot of stuff (including characters) so it is probably coming