Will your used Iphone work on Virgin Mobile USA's network?

With Virgin Mobile USA's (owned by Sprint) launch of the $30/month Iphone plan a lot of people are asking if there used Iphone from Sprint or another carrier will work on the Virgin network.  Otherwise you will have to pony up $649 for the 4S or $549 for the 4.  I emailed Virgin and asked this question and this is what they said:
Hello Todd,

Thank you for contacting Virgin Mobile Customer Care.

Let us apologize for any inconvenience this has caused.

In order to get our service, you need to have a Virgin Mobile iPhone. We
can not activate an iPhone that belongs to another provider. All phones 
are identifiable by Serial Number or MEID, our system won't recognize it
if it is not in our database. We appreciate your understanding.

If you need additional assistance, feel free to let us know how we can 
assist further or contact us at 1-888-322-1122 (or *86 from a Virgin 
Mobile handset). You can reach us Monday through Sunday from 4:00 AM ? 
9:00 PM PST. As a reminder, please make sure to include your Virgin 
Mobile phone number and PIN on all replies.

Thanks,

Deyanira
Virgin Mobile at your Service
www.virginmobileusa.com






So it looks like it won't work with them.