A method of operation of a radio access node (12, 16, 24) to enable multi-cast transmissions on a carrier in an unlicensed spectrum, comprising: performing (200, 500, 600) a Listen-Before-Talk, LBT, procedure on a carrier in an unlicensed spectrum prior to a multi-cast transmission that is to be synchronized with multi-cast transmissions from one or more other radio access nodes; and upon completing the LBT procedure before completion of respective LBT procedures by all of the one or more other radio access nodes, taking (206, 506, 606) an action to ensure that the multi-cast transmission from the radio access node (12, 16, 24) is synchronized with the multi-cast transmissions from the one or more other radio access nodes; wherein taking the action comprises either: deferring a start of the multi-cast transmission from the radio access node (12, 16, 24) until all of the one or more other radio access nodes have completed their respective LBT procedures such that the start of the multi-cast transmission from the radio access node (12, 16, 24) is synchronized to a start of the multi-cast transmissions from the one or more other radio access nodes; or broadcasting a preamble signal with a cell Identity, ID, of the radio access node (12, 16, 24) and one or more planned Physical Multi-cast Channel, PMCH, transmission burst parameters of the radio access node (12, 16, 24). performing (200, 500, 600) a Listen-Before-Talk, LBT, procedure on a carrier in an unlicensed spectrum prior to a multi-cast transmission that is to be synchronized with multi-cast transmissions from one or more other radio access nodes; and upon completing the LBT procedure before completion of respective LBT procedures by all of the one or more other radio access nodes, taking (206, 506, 606) an action to ensure that the multi-cast transmission from the radio access node (12, 16, 24) is synchronized with the multi-cast transmissions from the one or more other radio access nodes; wherein taking the action comprises either: deferring a start of the multi-cast transmission from the radio access node (12, 16, 24) until all of the one or more other radio access nodes have completed their respective LBT procedures such that the start of the multi-cast transmission from the radio access node (12, 16, 24) is synchronized to a start of the multi-cast transmissions from the one or more other radio access nodes; or broadcasting a preamble signal with a cell Identity, ID, of the radio access node (12, 16, 24) and one or more planned Physical Multi-cast Channel, PMCH, transmission burst parameters of the radio access node (12, 16, 24). deferring a start of the multi-cast transmission from the radio access node (12, 16, 24) until all of the one or more other radio access nodes have completed their respective LBT procedures such that the start of the multi-cast transmission from the radio access node (12, 16, 24) is synchronized to a start of the multi-cast transmissions from the one or more other radio access nodes; or broadcasting a preamble signal with a cell Identity, ID, of the radio access node (12, 16, 24) and one or more planned Physical Multi-cast Channel, PMCH, transmission burst parameters of the radio access node (12, 16, 24).