1. The bandwidth for BBC3 and 4 is used for the CBBC channels during the day, so that's why there is nothing on these channels during the daytime. They effectively run between 7pm and 6am.
2. Pages from BBCi as far as I'm aware would be impossible to broadcast. There are considerable differences between the services on DTT
and DSat for starters, and also I think the argument is that with Digital text it's so easy to select what you want to read, what's the point of actually broadcasting a cycle of pages from the service, like has been done with Teletext.
No neither of these new channels will broadcast a testcard or 'pages of BBCi' - which frankly I think is a good thing, the BBC should be filling the time with decent programming rather than sticking up some static card (except for any technical work which is understandable) and definately not something all digital viewers can get by default.
Teletext upto about 15 years ago was something only a few could access, so it was fair enough then to show a selection of pages so those without teletext receaving capabilities could see what the service had to offer.