So it does look like the shipping information is not accessible as a line item in script. Created a simple UserEventScript to render a PDF and that information isn't printing through the script. Now to figure out how to access the shipping information on its own and add it in the script!

Have you checked if it is a sublist on the record object?

in the records browser (http://www.netsuite.com/help/helpcenter/en_US/srbrowser/Browser2016_1/script/record/invoice.html) it shows shipgroup as a sublist but when we try to enumerate that sublist via our simple debug it's empty.

I assume you verified that the record you are testing has shipping lines.

Yes, we can see the data in a saved search as well as if we print the invoice through the UI it prints with the shipping line. It appears that only though accessing the transaction_lines for an invoice via script does the shipping lines not present in the data. My co-worker is exploring getting at the shipping line data as a seperate data source now to add it to the line items for rendering to a pdf via script