No, The Tantive IV diverts from heading towards tattooine and then Recieves the plans and then goes on to tattooine with the plans.

Tattooine is right next to Scariff for a reason.

Or they Simply Recieved the plans at a place near Tattooine it’s just as simple. It’s a transmission and it is a very big Dish on Scariff. People communicate with astronaughts all the time in outerspace.

Perhaps the Devastator showed up rather than the Tantive?

But it is of that effect as proved in the Re-written VR mission as the original ending with the Tantive was re-written.