Re: Hold on, if I read this right
Just like Google wants to lock you in in its data slurping ecosystem. Probably they went to iOS because they couldn't trust Android.
From a MS perspective, probably NYPD already uses Office, don't know what their mail system is, I wouldn't be surprised if it was Exchange already. ActiveSync is a documented protocol and many iOS and Android application do use it to communicate with Exchange. Other protocols (HTTP, SOAP, REST, etc) are fairly standard and there could be no issue to have an iOS app communicate with a Windows backend.
For the matter, NYPD has another project builf with MS, the "Domain Awareness System".