There must be one eHBL data transmission for each house bill contract of carriage. However, there are considerations made for shipments that are grouped at origin with, for example, one house bill with one shipper/ consignee pair and multiple vendors or suppliers. The vendor / supplier data is an importer responsibility. The shipper data on the house bill is the freight forwarder responsibility.
For example: The house bill contract of carriage could show: shipper: Canadian Retail X c/o ADB Consolidator, Singapore and the consignee Canadian Retail X. Historically, the CBSA has allowed this house bill scenario if title / ownership has transferred from the various vendors to the Canadian consignee prior to loading. Verify with the CBSA to ascertain if this applies to your customer.