Using "Manage Connections" I can select 1XEV to use Verizon or select GSM to use AT&T and switch between them in less than a minute, for voice and email coming from BES. However, each time I switch between networks, the icon for my non-BES email account disappears. Switching from AT&T to Verizon, I have to select the "Email Settings" icon, and enter my account password to "transfer" the non-BES account to Verizon that was there before switching networks so my email will show up again. When switching from Verizon to AT&T, the "Email Settings" icon is replaced by a "Setup Email Accounts" icon, and I have to go through the complete setup process each time.
Every time I switch carriers, I get a Blackberry Registration message, and apparently the registration process (which I understand comes from Blackberry through the carrier) removes access to my non-BES, personal email account