CPM Policy is Contractor's Part and Machinery policy.
Motor vehicles insurance policy is a different policy altogether.
However in Bajaj Allianz General Insurance v Ram Avtar case, the Delhi high court has said that it is not necessary to have paid additional premium for 3rd party liability when CPM policy is existent.
In the said judgment the Delhi High court has clearly stated that having CPM is good enough insurance cover as it includes 3rd party liability also.
In a case similar to yours more specifically in case of Bajaj Allianz General Insurance ... vs Ram Avtar Yadav & Ors. on 1 May, 2013 @ Delhi High Court, the Delhi High court has categorically stated as follows:
a) Excavator which is covered under Rule 2(ca) of the Central Motor Vehicles Rules, 1989, is reproduced as under:-
2(ca) "construction equipment vehicle" means rubber tyred (including pneumatic tyred), rubber padded or steel drum wheel mounted, self-propelled, excavator, loader, backhoe, compactor roller, dumper, motor grader, mobile crane, dozer, fork lift truck, self-loading concrete mixer or any other construction equipment vehicle or combination thereof designed for off-highway operations in mining, industrial undertaking, irrigation and general construction but modified and manufactured with "on or off" or "on and off" highway capabilities."
2b) In the present case, there was an insurance between the appellant and owner of the vehicle/respondent No.6 as per policy No.0G-10- 1101-0410-00000027 and amount of Rs.27,893/- was paid towards the premium. Though no additional amount has been paid in the instant case towards the third party liability, however, since the vehicle is covered under the Motor Vehicle Rules as a motor vehicle, the claimant / injured cannot be denied compensation under Section 140 of the Motor Vehicles Act, 1988.
Hence in your case, the liabilities arising out of the accident is covered under Motor vehicle rules as a Motor vehicle, CPM policy covers the claims arising out of the accident.
Hope this information is useful.