No, they don't boycott; they play hardball in negotiations:
"The DEAL project, headed by HRK (German Rectors' Conference) President Prof Hippler, is negotiating a nationwide license agreement for the entire electronic Elsevier journal portfolio with Elsevier.
[...]
In order to improve their negotiating power, about 60 major German research institutions including Göttingen University cancelled their contracts with Elsevier as early as October 2016."
"The DEAL project, headed by HRK (German Rectors' Conference) President Prof Hippler, is negotiating a nationwide license agreement for the entire electronic Elsevier journal portfolio with Elsevier. [...] In order to improve their negotiating power, about 60 major German research institutions including Göttingen University cancelled their contracts with Elsevier as early as October 2016."