Article 7 of the EU Package Travel Directive foresees that every member state has to ensure protection for consumers in case of insolvency of the tour operator.
Common ways are a coverage by an insurance company or a bank guarantee.
Details are regulated in the national law of each country.
In Austrian law package travel is defined and regulated in § 31b ff KSchG (Consumer Protection Law). The rules on insolvency protection however are mentioned in the so called Reisebürosicherungsverordnung (RSV). Unfortunately, there is no English translation of this act.
In order to be entitled to a refund of the paid amount if the tour operator goes bankrupt a consumer must be careful how much to pay when.
A downpayment of more than 20% must not be issued earlier than 20 days before the start of the journey and only by getting the travel documents in return.