Yes, it is. This is mainly because of the way Blackberry was initially designed: some of the Blackberry apps simply do not work without a SIM card. So we were forced to have the so-called BES5 –capable SIM cards; which are SIM cards for Blackberry handsets.
Secure Phone, on the other hand, does not suffer from that inherent restriction. This is why Secure Phone users may actually never use a SIM card; whereas Secure Blackberry users will always have to use it.
Yes, this is how it is. Without a BES SIM card you cannot have Secure Blackberry pushed on top of your Blackberry device
No, not really. The BES SIM card will only work with blackberry handsets. The opposite is true as well: The Secure Phone SIM card will not work with a Blackberry.
To clarify this question; you may never have to use voice minutes on Secure Blackberry. However you will need the SIM card for BES provisioning; and correct behavior of apps on the Blackberry device.