I have checked my source work based on The Irish Times 1859-1901 for No.18 Great Brunswick Street, Castlewood Avenue/Park/Place/Terrace and there is no reference to a Bryan Maguire
I note that No.18 Great Brunswick Street was Fagans Iron Works for most of the period you are interested in an wonder whether the Bryan you are interested in could have been an employee.
Regards Quaxer