The transmission lines on my 06 STR needed replacing for a few reasons.
1. Whilst disconnecting them from the radiator, I stripped the threads on the lower one. Jaguar chose to use an aluminium pipe nut screwed into a steel threaded insert on the radiator. Galvanic corrosion did the rest
. The nut on the lower line was completely fused into the insert, and the nut got trashed removing it from the radiator, despite using (gentle) heat, release oil and even freezing oil. 2. Once the pipe nuts were released it was obvious the tubes were trash anyway. The rubber to aluminium pipe joint that sit direcyly in front of the steering pump were freely rotating. So i figure the joints would be leaking and the crimps had failed.
3. This one is a bit more tenuous. While I was rolling about under the car, I noticed that the lower pipe had what looked like a longitudinal stress fracture. I might be wrong, as a finger nail test suggests its a raised ridge (manufacture defect) rather than a crack or scratch. When I remove them, I'll inspect them and report back. So I was dreading how much the tranny lines would cost to replace. Imagine my surprise when I was quoted £112+vat from Jag for the full assembly comprising of the two complete transmission lines including the 4 formed aluminium pipes, 2 rubber flexi's, 4 crimps and 2 plastic spacer blocks. What a bargain. Its still a shame jag didnt design and make the lines using more suitable materials in the first place tho'
because then I might not have needed to replace them in the first place 
. I'll try to remember to post the part number later.
Cheers
Steven