IJR, what you wrote is not completely true. I saw a demonstration of the XSteel <--> SAP2000 interface almost 2 years ago at NASCC show and the interface seemed to be working very well at that time... they were tranferring back and forth between XSteel and SAP a variety of different models, not just one. Tekla and CSI advertise that this link between their programs is solid, and based on the SAP2000 API.
However, as the original question was worded, SAP2000 cannot, from what I've seen, import a detailed connection designed in Tekla. SAP2000 treats connections as pinned, continuous or whatever using releases. It does not import details like bolts, gusset plates, etc.