The pipeline operators don't need to object in the Environmental...

The pipeline operators don't need to object in the Environmental Review Document, the relevant pipeline acts gives them the power to require anyone undertaking activities near a licensed pipeline an obligation to engage with the relevant owners to protect that pipeline from damage. That could be done in several ways - relocating the pipeline around the high risk activities, protecting the pipeline from those activities (i.e. concrete protection slab), relocating the high risk activity (could be the reason the trial pond moved, but it also may not).

Generally, agreements with pipeline operators are not reached until a project reaches an advanced stage of design, which I don't believe Mardie is at. Why would we assume that there is a major issue here that isn't being reported? Would that not have BCI falling foul of their disclosure obligations?

Your questions are relevant and interesting, but the simplest reason for why they are not expliciting answered in the reporting might be that BCI do not believe they are high risk issues based on their design information and conversations with the pipeline owners.

If you are as concerned as you say you are, why not simply ask the company? If it turns out there is a major issue and they still don't respond to it, there is then a record of being aware and not disclosing. Perhaps it will give you some piece of mind... or not.