Depends on what the AHJ says. Around where I am we always put them in and the Alarm company ones are optional. Sometimes the alarm company can put in a relay to work with you electrical smokes. They need to be brk smokes i am pretty sure. As long as all the smokes are interconnected the alarm company should be able to install the relay which saves you on buying 2 sets of detectors. So now your hardwired smokes are now part of your alarm system.