Around 600 APTs and senior teachers, whose posts are disappear in August, are being offered four options, against the two set out in the McCrone agreement.
But some staff believe they may never be able to climb the promotion ladder unless they "volunteer" for extra duties.
Many will be delighted that early retirement packages are likely to be available but others are angry that they may be forced to continue duties they believe should be within the remit of the reduced number of senior promoted staff.
Drew Morrice, Educational Institute of Scotland local secretary, said the union was concerned about members being invited to consider carrying out "duties similar to those you do at present".
"There is nothing specific in the document. The EIS nationally made it clear that the Yellow Book list of duties and annex B in McCrone are similar. The union does not accept this as a brave new world for teachers," Mr Morrice said.
The authority advises those concerned that they can apply for principal teacher posts, pursue the chartered teacher programme as they will be assimilated on to point 3 of its scale, or continue duties and be offered extra non-contact time. If none of the options are attractive, they will be considered for early retirement or winding down.
North Lanarkshire points out that staff cannot be given management responsibilities and would only be asked to continue duties that are listed in annex B of the McCrone agreement and can be done within the 35 hour week.
However, staff who contacted The TES Scotland remain unhappy that they may be asked by their heads to undertake additional tasks.
The EIS accepts that some members will opt into activities because they have always done them, although it remains suspicious of "management on the cheap". If there are jobs to be done, they should be worthy of principal teacher rank and job sized, Mr Morrice says.
No one from North Lanarkshire's education department was available to comment before we went to press.