The NCOS is on the trunk not the route; and I think 1brc is a little confused regarding targs and tgars - they don't have anything to do with the ncos.
The rule I learned is if they match the call won't go out. There is also the TGAR yes or no prompt in the esn data block that tells the switch if it should look at the targs and tgars or not. (look in NTP in LD 86 under TGAR).
I used to be very familiar with targs and tgars, but haven't used them in a while, so maybe someone else can help answer this for you. I can remember reasons that we used to put more than one targ on a route though - to block certain sets from going out that route, but allowing them to go out two other different routes. For example DN 5000-tgar 1 can't go out route 1, but can go out route 2. DN 5005-tgar 2 can't go out route 1 or 2 but can go out route 3. I hope I didn't confuse things even more!