Broadcast date are usually released about three weeks before transmission.
I think the reason for not saying when the programme is on right now, is the Beeb don't want ITV to put anything up against it.
About three weeks before transmission, details have to be released to the TV guides, so it is often too late to go changing the TV schedule.
You will find that closer to transmission, the start date will be included in the trailer.
I think this is a series. Can't wait, I read the books after seeing the one off last easter. My only very slight criticism is I think the lady on the Red Bush Tea advert would have made a better Precious Ramotswe - the one who tells the lions to be quiet you naughty boys!
I wouldn't be surprised if they schedule it at the same time as Lark Rise to Candleford, when that series finishes. I too am awaiting number two in the series. There are quite a few books so read them do!