Its extremely difficult to answer your question as it depends on how it is already wired what size cable it is etc
I assume its not wired 415v (unless its some large industrial unit) its wire 2 Phase.
One 240v Phase supplying the oven
One 240v Phase supplying the HOB (Hotplates)
If this is the case it would depend on the cable size and how its run.
I may be just a matter of terminating one phase at both ends and connecting the other to the new oven
But as I said its pointless suggesting things site unseen