Even if you are able to link to the new Merged File with 12 Split Tracks your going to have to recut the sequence anyway. Your timeline currently has a single Stereo Audio Track or two Mono Tracks and so the other 10 Tracks of Audio will not just magically show up in the Timeline. The Merged Clip doesn't have the same metadata as the unmerged clip does so Premiere sees it as a totally new and unrelated asset.
Unfortunately cuts should always be done with the merged audio right from the start. If the client couldn't supply this audio right away the cut should be held off or he should be paying for a recut when it does arrive.
"MY MEDIA/PROJECT MOTTO: If you think three copies of your Media or Projects are enough. Take a moment to place a value on them and then maybe add two more.
Hard Drives are now stupidly cheap. A RE-SHOOT AND YOUR TIME AREN'T."