The article mentions the MIPS/Ultrix-based DECstation 5000 series as systems that provide an ACCESS.bus interface. However, only systems from the Personal DECstation 5000 range (R3000-based models 5000/20,25,33 and the R4000-based 5000/50, codename "Maxine") provided an ACCESS.bus interface and the related peripherals (LK501 keyboard and VSXXX-BB mouse). I wrote the first Linux drivers for these in the 1990s and still have a number of Personal DECstations sitting in my basement...

If you want to experiment with ACCESS.bus, there's an app note from Philips (AN445, https://www.elenota.pl/datasheet-pdf/150926/Philips/APPLICAT...) and example code for an 8051-based ACCESS.bus mouse (http://www.microshadow.com/files/files8051/abmouse.zip).

The official ACCESS.bus specification can be found at https://archive.org/download/DECAlphaDocs (file names A.bus_spec_sec_[0-5]_v2_0.ps)