Can the DA be approved even if several neighbours object?

Yes. A Development Application can still be approved even if several neighbours object.

ACT Planning must consider all valid objections—formally called representations—received during the public notification period. However, ACT Planning expressly states that a DA decision is not based on the number of representations received. What matters is the content and planning relevance of the issues raised.

Relevant concerns, such as privacy, solar access or traffic, may influence the assessment and could result in further information being requested, conditions being imposed, changes to the proposal, or refusal. But several objections do not automatically prevent approval.

Reference: ACT Planning – After You Apply - https://www.planning.act.gov.au/applications-and-assessments/development-applications/after-you-apply