With what you wrote, I have a couple questions:
Are all of the plant logging to the same database or is the database the same name on each site?
How are the tag names the same? Are you just talking about the column name you gave them in the transaction group or the actual tag? To look at them all at once your tag paths would have to be different even if your using OPC addressing. If your creating tags in Ignition then they would still have to be unique in Ignition even if its just a line number that changes.
Did you build your tags using UDT’s?
Is the trigger a single value changes or any of a group of values?
The reason I asked these is if your looking at a group of values to trigger your transaction group you would have to have a way for your transaction group to know which one had a value change in order to collect the data. The issue I see is if 2 lines trigger at the same time, even if you have a way to tell it which one triggered, only one would be recorded.
I think you will have to do either separate transaction groups or you could do a value change script in your UDT, assuming you built one, that grabs the data and creates your entry. Either way is easy to do.
If your tag structure is the same and just has a line number that changes you can create a memory expression value for your line number then use the tag() expression function to get your value through other expressions instead of directly from OPC tags. Doing this you can make it ones then copy it for as many lines as you need.
Doing it through a value change script you can extract the line number from your tag path, assuming it is part of the path, to use for one of the columns you insert into your table, then you can do reads on the other values you need and run a named query to insert the data into your database.
All of this depends on how you have all your tags set up though. But where you listed your issue being that some of the tags have the same name, I’m not sure how that could be an issue since you would have to have a unique path either by your device name or something in your tag path.