Hello - don't know that this will help , but Penetration Management is the function within Catia for creating links between tube elements and regular CatParts. I have not found much use for it personally, it seems to be more for keeping track of an interface than actually being useful in any way for creating geometry.
Alternatively, if you go into Place Parts in Tubing Design, and place tube elements (straights and bends) on top of your tubing run, these tube elements, which act more like real catparts, may be able to be used to create linkable geometry - section cuts, centerlines, points or something?
It seems to me the tubing design package in V5, while I really like some aspects of it like being able to drag and drop bend points and such, works very poorly with regular CatParts and is completely divorced from the "Associative Design" functionality that is the real strength of V5.
I only hope that Dassault will continue to improve it and make it A LOT more user friendly.
On a related note, for extracting bend data, try the following - this was advice given to me and I have yet to try it: "Check out the V5 on-line documentation page 'Extracting Bending Data from Bendable Pipes and Tubes'. This explains how to use the Catia supplied PslTubingExtract.CATScript and PslTubingExtractTemplate.xls to generate bend data tables."
Good Luck -
Kelly S.