A couple of recent data points. If you travel with another person, you can receive the points for their ticket as well. At the ticket machines you have to do the purchase in one transaction, being careful not to apply the Bahncard discount to the 2nd person if they haven't got one.
I recently booked a 1st class Sparpreis for another person, for €39, and got the points on my Bahncard 25 account. I did it online, through my Bahncard account, and there was no discount applied to the 1st class Sparpreis. So, I conclude that I can get points for 1st class tickets using my BC25, but there is no discount. The other person (if you're absent) does need to show something as evidence along with the ticket, usually the credit card used for purchase, but in this case it was a German identity card (passports are not accepted).
Last edited by Concerto; Nov 6, 2014 at 1:44 am
Reason: missing info