Can an estate trustee recover their legal costs for defending a will even if they lose?

Sometimes, yes, though it isn't guaranteed. An estate trustee who reasonably and properly defends a will against a challenge, acting in the interests of the estate as a whole rather than for personal benefit, can often have their legal costs paid or reimbursed from the estate, even where the challenge ultimately succeeds — provided the court is satisfied the trustee acted reasonably in defending the will rather than pursuing the litigation unreasonably or for an improper purpose.

This isn't automatic, and it isn't unlimited. Courts scrutinize whether the estate trustee's conduct during the litigation was appropriate, whether they took a genuinely neutral, fact-finding role where that was called for, and whether continuing to defend the will remained reasonable as the evidence developed, rather than digging in regardless of how the case was going. An estate trustee who conducts themselves unreasonably, or who is found to have had a personal stake in the outcome beyond their role as trustee, can be denied costs recovery, or even ordered to pay costs personally. Because this depends heavily on how the litigation is actually run, an estate trustee facing a will challenge should get advice early about their proper role and how to protect their costs position throughout the case.