A Do-able project for in house, home automation that's unregulated and completely unsafe under OP's specs. To make it work one just needs to get a few parts, write a pm-util script, and follow guides on powering a Raspberry Pi by battery as listed below.
This is not my main account, so I do apologies for the lack of quality in the post's layout/link structure.
However, since I'm a big proponent of DIY COTS IoT projects especially ones using the raspberry pi. Thus I had to comment on this..
Power supply from 24-48 volt, that is the quickest way to start a fire! The RaspPi is a 3.3v 1.5A device (all versions as of 2015). The closest to an applicable resemblance to an IoT/Scada use case is on the raspberrry pi form itself https://www.raspberrypi.org/forums/viewtopic.php?t=36225.
Though the pi would still take a 5v rail only and anything more will let out the magical genie in very scarry ways.
Raspberry pi and safe shutdown is relative. Being that its a solid state device using a sdcard and depending on the distro configuration (ie debian or arch linux arm) could be using ext4 fs or something more fault tolerant(ie extreme datacenter usecase fault tolerant) as the filesystem.
One could write a pm-util script in python to send a signal over a GPIO pin for when the board enters into any of the ACPI power states: www.raspberrypi.org forums viewtopic.php?t=64051&p=473743
As for battery usage, there has been attempts to add battery power and solar power at that to different projects. Hackaday has a good write up on this at https://hackaday.io/project/5970-weatherpi-solar-powered-raspberry-pi-station
Just get yourself a Bud Industries AN-1302 case and some acrylic risers. Then drill the case for mounting to your din rail, custom built power supply, and pi board.
Other things to note
As everyone else has pointed out on this post the Raspberry Pi is a cheap COTS "pc" with GPIO boards designed to be an educational tool or simple DIY toy in the same spirit as the old TRS-80/C64/Altair 8800. Any resemblance to an actual end product is only relative to one's licensing with the "RASPBERRY PI FOUNDATION" and Broadcom. Plus these boards and custom project would not be UL licensed or safe in any fashion for scada environments as defined by most governing bodies. Therfore if it breaks or damage anything then as with all in house built solutions; one has to remember it is your team's responsibility to support it.
All in all using the same design concepts highlighted here would be great for one's makerspace or home automation. Plus, if your hire-ups are willing to back the use of a DIY solution then all the more power to you.
Earned a few points so now I'm able to use advanced editor options and clean the response a bit.
There is a raspberry din rail case instructable available.