There were many projects using Pi Calculus, too. One of my project ideas is something that converts TLA+ to SPIN and Pi Calculus to use their tools and works. Or just otherwise integrates them.
I don't think TLA+ is far too expressive to translate to Promela. There are, however, tools that translate subsets of TLA+ to ProB: https://www3.hhu.de/stups/prob/index.php/TLA
http://spinroot.com/spin/whatispin.html
http://www.imm.dtu.dk/~albl/promela.html
There were many projects using Pi Calculus, too. One of my project ideas is something that converts TLA+ to SPIN and Pi Calculus to use their tools and works. Or just otherwise integrates them.