Well, one way is to use a number of invisible H Pads as the getPos points for each explosion. If you give these invisible objects (or IED objects, whatever) a probability of presence, you should get the same result...
put this in
IED1's trigger on Act.
Bomb123 = "Bo_GBU12_LGB" createVehicle (getpos IED1);
then in
IED2's trigger on Act.
Bomb123 = "Bo_GBU12_LGB" createVehicle (getpos IED2);
etc, etc
then simply give each of your IED's (editor placed object: invisible H Pad, IED looking object, etc) the desired probability of presence %
If you can find a good IED object to use (there are a few addons out there available), it could be an editor placed log, barrel, wreak, or even a rock. Just be careful not to make the object to obvious or else they will be easier to spot than a Mine in the middle of the road! Try to blend them in or disguise them as real Insurgents do! This in my opinion is the more realistic way to go, as by setting each objects Probability of Presence, the object is either there or not. If the IED object ain't there, the trigger will still activate for each, but nothing will happen as the explosion has no object to 'getPos' to