Google effects of a domain change

[asans]

What if a company which owns some portals, all with a lot of traffic and with an high PR, decides to transfer all the singles domains of the network under an unique domain, creating in some way an unique great portal with many subdomains?
In this case, should we use 301 permanent redirect, to allow main domain to gain the PR and the link popularity from the old domains?
The change will be that:

Old domains:
www.olddomain1.com
www.olddomain2.com
www.olddomain3.com

New domain, already existent with the corporate site on it:
www.maindomain.net

www.olddomain1.com ----> olddomain1.maindomain.net
www.olddomain2.com ----> olddomain2.maindomain.net
www.olddomain3.com ----> olddomain3.maindomain.net

Using a 301 redirect, does the subdomains get PR, link popularity and google keywords ranking positions?

Thanks in advance,
Alex

[Stefan]

I would be worried about it being "sandboxed". Major URL changes like that seem to have caused problems during the last year, even with the proper redirects applied. I'm no expert on what you're suggesting, but I think there's a chance you might lose all your traffic for many months by doing it. If anyone knows that I'm wrong on this, please correct me.