Hi. Tarkin's upgrade says this:

Can Tarkin's friends lock Tarkin's locked ship even if that ship is beyond range 3 of them, and in normal conditions? (No Jendon effect in play).

No. Acquiring a lock has a 0-3 range restriction, regardless of the source, per "locking" in the rrg.

Contrast with Dutch, who specifically allows you to ignore range restrictions on locks:

Also of note is that Tarkin doesn't combo with Jendon anyway - Tarkin triggers before Jendon, so he can never benefit from Jendon's ability.

Thanks.