1. You are not supposed to board at any technical halt. (De-boarding is still allowed unofficially)
2. I am sorry for my earlier reply. I did not notice that IGatpuri falls before Bhusaval.
Yes, in that case you can board at Igatpuri. If any berth is empty, the TTE would allot you the same and also charge you with a fine. The train...
more... should reach Igatpuri around 11 pm. (Thus it can be contemplated where TTE would be present for checking the tickets that time)
Anyways, you can definitely try your luck. Do not forget to purchase the unreserved superfast ticket. ALso keep some amount to pay for the fine as being charged by the TTE.
If no berths are available, board the Unreserved Compartment and return back to your allotted coach at Bhusaval.
Regards.