If the SOLIDWORKS part was saved as a STEP file ('dumb solid') or the bodies were saved out (using save bodies or insert in to new part) then you wont see the feature tree by default. Is there a reason you require this? The part may have been defeatured to protect IP etc but here are a couple of suggestions:
1. For the STEP geometry imported you could try to use FeatureWorks Add In (under Tools > Add-Ins) to try to recognise any simple feature like fillets, holes etc but this will only automatically recognise some feature with some manual tweaking required. You may need to split the bodies and rebuild some of the smaller more complex features which will depend on the complexity of the part.
2. With the Save Bodies (for multibodies) command or Insert in to new part, if you could find the original SOLIDWORKS part reference by right clicking on the body and choosing List External References or ask the user to save the body but include some more reference information (like planes, features, origins etc) if the references are broken to the original using the option in the 'List External References' window.
Try these methods and one of them may work for you.
I try this, doesn't work unfortunately