The routine for an unplayable tackle is the same as far an unplayable ruck.
Not necessarily.
There are subtle differences. There is an extra option for the ref to consider with the ruck that he doesn't have with the tackle.
Law 20 Scrum
20.4 The team throwing the ball into the scrum
(a)
After an infringement, the team that did not cause the infringement throws in the ball.
(b)
Scrum after ruck. Refer to Law 16.7.
(c)
Scrum after maul. Refer to Law 17.6.
(d) Scrum after any other stoppage. After any other stoppage or irregularity not covered by Law, the team that was moving forward before the stoppage throws in the ball. If neither team was moving forward, the attacking team throws in the ball.
Law 15 Tackle
15.8 Doubt about failure to comply
If the ball becomes unplayable at a tackle and there is doubt about which player did not conform to Law, the referee orders a scrum immediately with the throw-in by the team that was moving forward prior to the stoppage or, if no team was moving forward, by the attacking team.
Law 16 Ruck
16.7 Unsuccessful end to a ruck
(a)
A ruck ends unsuccessfully when the ball becomes unplayable and a scrum is ordered.
The team that was moving forward immediately before the ball became unplayable in the ruck throws in the ball.
If neither team was moving forward, or if the referee cannot decide which team was moving forward before the ball became unplayable in the ruck, the team that was moving forward before the ruck began throws in the ball.
If neither team was moving forward, then the attacking team throws in the ball.