Eliminating an Inner Query when using UNPIVOT

In the following query, I am attempting to UNPIVOT a number of different phone / fax numbers into a single column named 'PhoneNum'.

I haven't used UNPIVOT before, and I'm trying to understand a couple of things about it:

1. Why does the query run without error if I alias the outer select list with 'work'?
2. Can I write this in a way that I can eliminate the inner SELECT?

The following is the query I am working with:

SELECT DISTINCT
program.RecordNumber
,work.PhysicianEntityKey
,program.insurerKey
,work.ParFlag
,work.ProviderID1
,work.ProviderID2
,work.ProviderGroupID
,work.ProviderGroupName
,work.NetworkID
,work.EffectiveDate
,work.TerminationDate
,pn.PhoneNum
FROM 
( 
SELECT distinct
RecordNumber, 
InsurerKey, 
PhysicianEntityKey,
ParFlag,
ProviderID1,
ProviderID2,
ProviderGroupID,
ProviderGroupName,
NetworkID,
EffectiveDate,
TerminationDate, 
PhysicalPhone, 
PhysicalFax, 
cast(BillingPhone as VARCHAR(10)) as BillingPhone, 
BillingFax 
FROM PMR_ETL.Provider_Work
) as  iq

UNPIVOT ( PhoneNum FOR PhoneUseType IN (iq.PhysicalPhone,
                                                iq.PhysicalFax,
                                                iq.BillingPhone,
                                                iq.BillingFax)) as work

LEFT JOIN Physician.Nexus pn
ON pn.NexusHashValue = CAST(work.PhoneNum as VARBINARY(40))
LEFT JOIN ProviderODS.Physician.Nexus ods
ON ods.NexusHashValue = CAST(work.PhoneNum as VARBINARY(40))
INNER JOIN PMR_ETL.Provider_Program_Work program
ON program.RecordNumber = work.RecordNumber
and program.InsurerKey = work.insurerKey

I hope I have communicated enough detail about my issue. Thank you for your help.