Union officials are holding urgent meetings with the firm expected to take over Brighton and Hove's bin collection and street cleaning.
Pensions and the use of agency staff are key issues.
The proposed takeover by Serviceteam from current contractor Sita on October 1 means some of the workforce would have had five different pension schemes in the past four years.
As French-owned Sita has been operating in Brighton and Hove for less than two years, the dustmen and street cleaners who decided to sign up for the scheme have not been able to build up worthwhile pension contributions.
Some of the workers are cashing in their contributions to the Sita scheme, incurring financial penalties Yesterday GMB officials held a meeting with some of the 250 staff affected by the constant changes.
Union official Gary Smith said he was hoping problems could be resolved with Serviceteam.
He said: "We want to ensure we do not get off on the wrong foot with Serviceteam. There is real concern among our members about pension provision. As yet there is nothing in its place.
"The current situation is completely unacceptable. We have members who will have had five different pension schemes if Serviceteam takes over.
"There is a real prospect of some of our members having eight or more pension schemes by the time they retire."
"There was exactly the same problem when Sita took over in 1999 and the company's failure to provide an adequate pension scheme led to demonstrations and soured industrial relations."
The situation with agency workers and how many Serviceteam will have to employ has also not been resolved.
Mr Smith has brought the problems to the attention of council leader Ken Bodfish.
A spokesman for Serviceteam said: "Everything is going well. We are still in negotiations with the council and workforce and everything is set to ahead for October 1."
Comments: Our rules
We want our comments to be a lively and valuable part of our community - a place where readers can debate and engage with the most important local issues. The ability to comment on our stories is a privilege, not a right, however, and that privilege may be withdrawn if it is abused or misused.
Please report any comments that break our rules.
Read the rules hereComments are closed on this article