This means obtaining interim approvals:-) For example, obtaining singatures of all technical specialists before the Chief Designer signs (approves) it.

BTW, this changes the idea of сопровождение, doesn't it?

This might be what you're looking for if unanimity of opinion is required (such
as for technical reasons)

This is the process of obtaining various PERMITS from various federal and municipal bodies - ...участвовать ... в согласованиях - means literally "to participate / to take part along with the Client in the process of obtaining necessary (construction) permits.

Permits may include: - permit to build building of such and such height; - permit from geologists to use such and such site for constrcution of such and such building; permit to drill a well if needed; - permit to do excavations onsite (which, say, may include confirmation from archeologists that there is no any old artefacts around, etc.); then - when we have a building already - there will be a permit from municpal inspector on electrical, hydro, more.

It's a normal process which exists in probably every country.

The requirement in question - about Contractor.. TO PARTICIPATE ALONG WITH THE CLIENT IN THE PROCESS OF OBTAINING NECESSARY (CONSTRUCTION-RELATED) PERMITS.. could be done simply because Contractor can have more professional knowledge than Cleint in many aspects of construction thus the Contractor's participation would benefit the project.