The subpoena requested "all routers used in connection with the November 3, 2020 general election"; so I guess it could arguably cover routers outside of the EMS.
That said:
#1 It's unlikely that the AZ senate has the votes to hold the county in contempt at this point (the audit has only gotten less popular over time).
#2 They want to avoid handing them over for security / privacy reasons (they've mentioned a few times the sheriff's department has concerns -- nothing concrete but c'mon who among us would be happy to hand over a ton of info about an intranet we're in charge of).
To put this all in context: the county took a much more aggressive position against the audit after the audit twitter account accused them of deleting a DB file to hide evidence and the AZ senate was about to drag them into a hearing they planned to broadcast on OAN. In particular the county has done an incredible job of countering misinformation with facts on their twitter account.