There is overload protect but not individual short circuit or ground fault protection provided by an OCPD ahead of the each starter. Basically you have a control panel designed for three motors with an individual circuit for each motor. Electrical drawing showed a single control panel with one circuit feeding the entire panel so only one circuit was pulled. Now they want to simply splice onto the larger circuit conductors (#4 I believe) with #10's and feed the three motor starters within the control panel.
This concept is used all the time, but for MUCH SMALLER MOTORS. The reason is because if you are dealing with 3 x 1-1/2HP 460V motors that each are 3.0A FLC, then all 3 loads together still are small enough to fit behind #14 wire, the minimum size anyway, and a 15A circuit breaker.
The #4 conductors are (I assume without looking) OK, especially in that you will need a larger feeder for that circuit because of the potential of 3 fully loaded 10HP motors on it, i.e. 52A minimum. So assuming a 70A breaker, that becomes your GF/SCPD for the ENTIRE circuit. The individual OLs can count as the OCPD for the motor conductors, but not the GFSC device. So that means that TECHNICALLY, this can only work like this if you run the #4 all the way down to the motors, which will most likely be a big problem once you get to the motor peckerhead.
One way to do this though is to use the IEC style Motor Protective Switches that each have the necessary circuit components. They are the SCPD, the OL and a Disconnect device all in one. So that plus a plain contactor makes an individual Combination Motor Starter for each circuit. There are other rules that you must pay attention in the NEC if you do this, but it is possible.