Good practice to shoot the off-speed material on separate tapes from the 25fps material.
Frame rate of recording is recorded in user bits.
I recently got a per-tape quote of £120-240 for 30min HD varicam @ 60fps -> 72 min SD Digi @ 25fps via Panasonic Frame Rate Convertor.
I haven’t tried capture via Kona or firewire. I understand there are issues getting FCP to control a 60Hz deck in a PAL project, also that the firewire option doesn’t use the CineGamma curves that the Varicam Deck applies on Baseband output (i.e. you need to do your own colour correction to get the VariCam look).
The FCP software FRC may, or may not, work – I’ve read differing opinions on this.
It is possible, I believe, to get the Sony HD Cameras to record at 50fps then playback at 25fps.
HTH
Trevor