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

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.
subsidiary