Can Sketchup Pro 8 use a network-license file from a previous version of SketchUp?

No. However, to upgrade your SketchUp network-license environment to SketchUp Pro 8, you can follow these steps:

1. First thing first, you'll need to upgrade your license to Sketchup Pro 8. To take the leap, visit the "Upgrade" section of the Sketchup Store.
2. Install SketchUp Pro 8 on all computers that are using a previous version of SketchUp. Visit our download page for the link.
3. Open the email that contains your SketchUp Pro 8 license (i.e Serial Number and Authorization Code).
4. Launch SketchUp Pro from one computer.
5. When the Welcome window opens, click the Add License button. If the Welcome window doesn't open, start using SketchUp and click Help > License > Authorize.
6. Open the license confirmation email that you received shortly after purchasing your license.
7. Copy and paste your User Name, Serial Number, and Authorization Number into the dialog box.
8. Click OK.
9. When prompted, browse to your shared license folder. You may want to create a new folder in order to keep your different version license files organized.
10. Click OK.
11. To authorize the other computers:
    
    1. Close all instances of SketchUp to avoid reaching the maximum number of license seats during the authorization process.
    2. Launch SketchUp Pro on one computer (we suggest authorizing one computer at a time).
    3. Click Help > License > Set Network License file.
    4. When prompted, browse to and select the shared license folder that contains the new "SketchUp8.lf" license file.
12. You can uninstall older versions of SketchUp if you'd like, but SketchUp Pro 8 and previous versions of SketchUp can co-exist on a computer without conflict.