Hi Amar
GIS - Consider using NWBC as the user interface instead of GUI which gives you a flexibility to use side panels. So you can link GIS with the side panel.
SCADA/DCS or similar systems - There are two things that you can integrate at least: alarms and measurements. Alarms - can be converted in to notifications and measurement can be filtered and used to generate measurement readings as well as notifications if you are planning to use Condition Based Maintenance. As measurement readings are usually saved ina data historian, you can report these in BI too for trends analysis.
We used SAP MII for the interface.
Regards
Savas