Dear friend,
As far as I know,
1) No statutory mandate in the Employees Compensation Act,1923 for taking up insurance policy against injuries caused to employees due to employment accidents.However, if the employer is a owner of a motor vehicle, S 146 of the Motor Vehicles Act, 1988 mandates a suitable insurance policy in respect of third parties' risk arising out of the vehicle's use in a public place.S 147(1) of the M.V.Act makes it obligatory for the insurer to cover the liability under the E.C Act,1923 in respect of death or bodily injury of an employee arising out of n in the course of employment and such a liability is with regard to the available compensation under the Act.In other words the insurer virtually steps into the shoes of the employer for the purpose of paying the compensation to the workman.In case you are a Contract Labor Establishment, your Principal Employer can insist an E.C.Insurance Policy in respect of the contract labor you are going to supply.If the contract is very dear to you, u have to take up an insurance policy accordingly.
2)As it is, there is no legal compulsion to take insurance in respect of all the workmen likely to be actually employed.Since insurance is virtually a contract between the employer n the insurer, the conditions are to be discussed n decided mutually.Normally, unnamed insurance policies are taken in respect of workmen category-wise depending upon normal requirements of any work.
The necessity for quoting judgments arises only in case of practical ambiguities and I do hope there is none regarding your queries!!!