Thank you all for the comments.
Lash-ups.... I still love it. Despite my partner's protestations, and despite a lot of conversation to the contrary, it is STILL the term used by my good friend who has worked for CSX as an engineer for the past 25 years (and he still uses it regularly to this day). He also says that most if not all the other engineers he works with still commonly refer to one or more engines "MU"d together as "lash-ups". 
