I've got BIS on both T-Mobile UK (BlackBerry 8700) and Orange UK (Nokia E90 with BlackBerry Connect). I also have BES with the second but let's leave that alone in this thread!
Adding a standard @gmail.com / @googlemail.com email account to either BIS functions as it has done for ages, with no requirement for inputting POP3 settings nor are POP3 settings configurable in the BIS interface under any Advanced Settings tab as they are if you add, say, an @mail.com email account or other "ordinary POP3" email account. Email is pushed to @gmail.com / @googlemail.com accounts instantly. I've noticed that setting up one of these accounts enables POP in the Gmail /Googlemail settings on the web interface. Despite this, there is no delayed polling so it doesn't appear to be "ordinary POP3" in use.
Adding a Google Apps / Google For Your Domain hosted email account, utilising a custom domain name, now works in the same way as above. There is no prompt for POP3 settings and those settings are not configurable under any Advanced Settings tab. Email is pushed to these accounts too. POP in the web interface is enabled however, like with the above, there is no delayed polling so it doesn't appear to be "ordinary POP" in use either.
A few points:
(i) Deleting an email on either the device or in the web mail interface does not delete the email on the other.
(ii) Email sent from the device does appear in the Sent Mail folder on the web interface.
(iii) Deleting an email from the sent box on the device does not delete it from the Sent Mail folder on the web interface even if it was sent from the relevant account configured on the device.
(iv) Email sent from the web mail interface appears in the Inbox on the device within the relevant account, rather than in the main sent box on the device. I believe this is down to how Google deal with email because you can see both Sent and Received email underneath the All Mail folder in the web interface.