In June, we announced that the LUMA Energy, a joint venture between Quanta and Canadian Utilities Limited and ATCO company, was selected by the Puerto Rico Public-Private Partnership Authority for a 15-year operation and maintenance agreement with the Puerto Rico Electric Power Authority, or PREPA, to operate, maintain and modernize PREPA’s more than 18,000-mile electric transmission and distribution system in Puerto Rico.
Take context from the input text and decide on the accurate relationship between 'ATCO' and 'Canadian Utilities' from the options provided.
Options: subsidiary, stock exchange, operator, legal form