Looks like max 50GS/s per their site. That also looks reasonable with the screenshot they have in the article showing 1ns / div horiz. But clarity on the data would be lovely. =)
Actually I take it back:
For the series 6B spec page...
Real-time: 50 GS/s (2 channels), 25 GS/s (4 channels), 12.5 GS/s (> 4 channels)
Interpolated: 2.5 TS/s
Yeah, I used to work at Tektronix, this looks like an A unit.
Also, the 50GS/s is actually more like 25GS/s as it has a Nyquist frequency of 12.5 GHz.
This is because they take 2 samples at the same time, instead of 180 degrees out of phase.
I wish they had made that clearer to customers, it felt misleading to some.