Yes, you have insurance coverage if you need to take your pet to a veterinarian in another country. The costs for the treatment, which is covered by the pet health insurance, are limited to the reimbursement level that applies to a veterinarian based in Germany in accordance with the fee schedule for veterinarians (GOT).
*This applies to temporary stays abroad. There is insurance coverage for up to 12 months worldwide for each uninterrupted stay abroad.