Subcontractors and contracts between client and prime contractors

[Insanity]

Is it ever appropriate for a Subcontractor to ask a prime contractor for the statement of work between them and the end client?

Simple background -

I'm getting some conflicting information and want to get a clear understanding of what the existing contract is between the prime contractor I am subbing for and the end client.  Is there a way to do that without going over the line?

[BlueHouse]

For me, it's always appropriate because I'm a program management consultant and I'm helping the prime manage their contract with their customer.
Although there is no legal basis for you to compel the prime to share, it usually helps to understand what the prime's specs requirements and curls are.
Also, if it's a govt client, the contract should be publicly available and the sow may be incorporated into the contract or at least the rfp.