Following on from the SD feeds, the BBC are now testing 16 Olympics HD channels - 4 per transponder - of "test slides" (excerpts from various BBC TV shows) on various Astra satellites. I've tuned into them using the KingOfSat list - find the lines with a green HD box and use the sorted SID (in tvheadend) to allocate a channel name - and a few are giving me bad signals for some reason.
And, yes, Bjork is mixed in there again!
The 4 HD channels per transponder (meaning up to 6 transponders could be used to cover 24 HD channels) does confirm that you'd need two quad tuner cards to guarantee recording every one of the HD channels at least once. It's likely most days will have less than 24 simultaneous channels broadcasting, so it is possible to double up on some sports, though trying to plan which events will be on which transponder could prove complex!
My thoughts are that you record on 3 tuners on each card (doubling up across the "important" sports if there's any spare capacity) and then use the spare tuner on each card to record the remaining BBC HD channels (BBC One HD, BBC HD and the new HD channel that cropped up recently) twice over. The terrestrial tuners can then cover all the SD stuff (BBC One, BBC Two, BBC Three, Red Button 301, Red Button 302, BBC News - and maybe Sky News?) twice over.
Yes, the SD recording will almost certainly duplicate the HD recordings, but since it only uses 25% of the disk space of the HD channels, it's worth doing in case something goes wrong with the HD transmissions. Don't believe that could happen? BBC One HD went completely off the air for 20-30 minutes during Andy Murray's live Wimbledon quarter-final match this week (I know, because my system recorded the caption shown in the BBC article) and yet BBC One SD was fine!