Mitel's purchases of InterTel, Aastra, and Shoretel were executed with boasts of synergies that resulted in massive job losses and attrition. Those companies also had overlap but not on the scale of a behemoth like Avaya, nor did they carry the debt load Avaya does.
Bloomberg reports they expect synergies of at least 250 million per year. Given the 100% overlap of the two companies, Mitel 3100 employees, Avaya 8200 employees, it's safe to assume that the 'synergies' will mostly come from permanently removing salaries from both companies. 250 million/year can be estimated to be at least 2500 north american and euro jobs, likely more. Asian employment will increase as Mitel's Dallas based management's long term strategy is to offshore R&D jobs to India and manufacturing activities to China. Mitel's executive management team is very proud that they get in front of economic recessions by ruthlessly cutting staff as soon as they feel a sales chill. Pray that Trump is right and the good times will keep rolling, better yet, pray that a better suitor comes along.