Greetings,
Yes - MTRX and MTRX Studio both include a DigiLink license which are redeemed when you register your unit online at Avid.com. Yes - I would certainly ask the party you are looking to purchase the hardware from if they can transfer the DigiLink IO License, else you will need to purchase one to use it with your system.
For transfer of ownership -> go here:
https://avid.secure.force.com/pkb/articles/FAQ/en363631
best,
Jeff