What's the bargaining space in a post-doc employment contract - in the Netherlands?
Legally, as far as I understand, it is not possible to negotiate new terms that contradict the terms of the applicable collective labour agreements in the Netherlands. Many labour agreements however leave some room for negotiation, see e.g. Appendix 3 in the file you linked. In practice however there I would not expect there to be much room.
As for your example questions:
As Bill Barth pointed out, Section 1.9 arranges IP ownership, and indeed the employer owns everything. See also point 4 of Article 1.9.3. I don't see much room here for negotiation.
This is not part of the collective agreement. Your contract may have certain provisions, for example the amount of teaching (if applicable). You should discuss this with your supervisor/boss on what is expected and how much freedom you will have. Here there may be some room for negotiation.
Again, this is something the supervisor can answer. It depends on how much budget the group has available, or if your work is part of a grant funded project, how much there is available there.
Looking at the collective employment agreement briefly, I'd say that pretty much everything is prescribed, and that only the things in Appendix 3 are negotiable. That is to say, you can negotiate about some things in the amount of gross salary and the amount of vacation. These are options for, it appears, trading salary/vacation for help with commuting costs, costs of school, union dues, additional retirement savings, and the purchase of a reasonable bicycle (it is the Netherlands after all!). This is referred to in Section 1.8 of the General Provisions.
Section 1.9 of the General Provisions covers Intellectual Property. I don't see anything that makes these provisions negotiable, and the employer appears to own everything. 1.9.2 covers Copyright and 1.9.2.1 covers requests for the transfer of copyright to the employee. If you are concerned about who owns your scientific articles or software products, I would ask how frequently these transfers are approved.
I haven't looked through all the chapters for provisions specific to researchers and postdocs, so if you are concerned that you might be assigned duties outside of your own, self-directed research, I would carefully ask your interviewer/potential supervisor about that. Post-doctoral positions are usually about extended training in the US, and so they tend to be a blend of producing works that came out of the dissertation (or extending it) and producing new works that are a collaboration between the postdoc and the advisor. I.e., postdocs are expected to continue working on their old ideas but also work on new ideas that come from the collaboration of the postdoc and the advisor.
That's the theory at least. They are often expected to do the former and also lead ongoing lab efforts at the advisor's sole direction. If you are concerned about this, ask. Just be careful that you don't turn your potential employer off to hiring you due to an apparent unwillingness to be a team-player.
In hindsight, I can say the following:
The research institute did not take kindly to attempts at negotiation, and would basically not negotiate on nearly anything. (That is, it's not that it stuck to its position - there was no negotiations dialog).
Exceptions or near-exceptions to this rule were (or could have been):
- Mode of calculation of your effective experience (e.g. how does industry experience count)
- Guarantees regarding funding for experimental equipment
- Opportunities for "access" to potential grad students
- Some kind of help with temporary accommodation while you search for a place to live in Amsterdam, which is an incredibly long and arduous process.
- (Informal?) agreement re how FOSS code you write is to be licensed upon release
Perhaps there are a few other negotiable points, but the negative attitude to negotiations makes it difficult to cover that many.