You could capture via the composite BNC if nothing else. The decklink should control the machine as it’s standard “BVU-800” protocol VTR. There are breakout cables kicking about here in the US, but you could build yourself as the standard betacam components Y: 1.0Vp-p, 75 ohms sync negative R-Y: 0.7Vp-p, 75 ohms B-Y: 0.7Vp-p, 75 ohms are present on the pinouts – just wire these to BNCs and it should work.