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Once you have "fixed" the samplerate by recording some audio data at the project settings, Sonar will auto convert any audio you drag into the project or import otherwise.

I really do not remember if SONAR 8 could do sample rate conversions on import. But I know that R8Brain is a well respected free application to do this and can do it on a batch of files at a time.
 
http://www.voxengo.com/product/r8brain/
 

Open the project with the 48k clips, then export the individual tracks as 44.1k wav files.  You can choose whether to retain track mute / envelope / fx data or simply export the files raw.  These can then easily be imported into your 44.1 project.  In terms of time alignment, the most foolproof method is to export from Time = 0.

I would have thought S8 already did auto-conversion of sample rates by File > Import if not also by drag 'n' drop Otherwise, you should consider an upgrade; all other methods will require extra steps.
 
EDIT: I just checked the 8.0 Ref Guide and confirmed for File > Import:
 
"If the sampling rate from the Wave file does not match the sampling rate in your project, then it will be converted to
the current project’s sampling rate and bit depth."

Since you've already established that direct copy-paste isn't supported, I think your best alternative will be something like this:
 
- Drag clips from the source project to a system folder - they'll be exported with file names based on the track names at the source sample rate.
- Set Now time and track focus in target project, and File > Import > Audio from the system folder.
 
 
 
 
 
 
 
 

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