Yes you can. You will need to have a single A2X user account with access to both A2X accounts that you want to share Xero access. One account connects to Xero normally. The second account will 'share access'. 


To share access in A2X settings you can reset the Xero connection, and select the option 'If you would like this A2X account to access the same Xero organization as another of your A2X accounts click here' instead of connecting to Xero normally. This will allow you to select the first A2X account as the shared Xero access for the second account.