How to access data from a Mac Contacts backup: a .abbu file

After I back-up Mac Contacts to a .abbu file, is there a program that lets me get at the underlying data vs. just importing them? I.e., can I open them as a text file or .CSV. Thank you!

In Contacts Version 8.0 (1371) running on OS X 10.9.4, you can export a multi-card file in the .vcf format as follows:

1. Launch the Contacts application.
2. Ensure that all your contacts are showing by clicking "All Contacts" in the Groups panel. (If you don't see the Groups panel, which starts with "All Contacts," on the left side of the window, choose View > Show Groups from the menu.)
3. Click the first contact on the contacts list.
4. Choose Edit > Select All from the menu. Ensure that the card detail area on the right shows how many cards have been selected (e.g., "612 Cards Selected").
5. Choose File > Export > Export vCard...
6. Enter the desired export filename and location, and click Save.

You will now have a single .vcf file with all of your contacts. This is a text file which you can open with TextEdit. You may also find tools that convert .vcf to other formats, such as .csv, if you need it.

This .vcf file can be used to restore your contacts or migrate them to other devices.

If you have iWorks/Numbers installed, check the tutorial:

How to Convert an Address Book ABBU File to CSV

ABBU is the native file type for the Mac OS X Address Book, which means that you can only open ABBU files using the Mac Address Book application. However, you can use the iWork Numbers application to import the ABBU file, and then export the data file to a Comma Separated Value, or CSV, file format, which is a generic text file format that you can import into any address book or database application, regardless of operating system.

Also you could try the tool:

AB2CSV

Also known as Address Book to CSV Exporter, this Mac OS X utility allows the user to export his own Address Book in a CSV or VCF file.

You did mention "vs just importing them", but if you can use the first method to export them to Numbers, you can then save as .CSV.