Yes you could. 
Depending on what sonar you want to share will dictate which 800 series unit you will have to purchase: 
 - If you want the Si and or Di sonar from the transom mounted HDSi transducer up front; your only choice is the 898c Si unit.  Be sure to set the Transducer Select/Connected Transducer menu to the “Universal Sonar 2” setting when using the Terrova’s transducer and back again to the “Hi-Def Sidescan” setting when using the sonar data from the 898c Si unit. 
 - If you only want the 2D sonar from the transom mounted HDSi transducer up front; you will need the 858c model unit. 
To buy a unit minus the transducer, you need to look for a “CHO” designated unit (Example: “898c Si CHO”).