They are being very secure as far as this one goes.
Yes, the shiny Milotic is a wonder card event, and you can only get it if you decide to participate. You have to have Platinum only, and you give your game cart and DS (except DSi, then just cart) and they put in an event cart in the GBA slot (Looks like a dark grey Drill Dozer cart). And yes, they check for the legality of your cart as well.
Here are some stats for the Milotic -
Shiny
Timid - Forced across all Milotics
Flame Orb
-Rain Dance
-Recover
-Hydro Pump
-Icy Wind
Caught in Cherish Ball
255 Beauty and 150 Sheen
Met at LV 50 - Pokemon Event - Fateful Encounter
Classic Ribbon
OT - VGC09 / Male
ID - 5099
SID -14128
IVs Randomized
F4 on 46h and 0B on 47h
And here's a nice little thing, legal.exe says it's hacked as its type, everything else is good though.
There was a 2/5 chance of someone being picked because of the turnout for Seniors, and the machines used for official matches were interesting:
You place the cart in a white box(Stack 3 Wiis flat on each other, then get another stack and put the stack's back together, thats the approimate shape/size), and it has a special cord coming of the side to connect to a DS lite's DS slot. These boxes can output the matches to TVs, force the wireless functions to the person also connected to your box, and possibly perform checks. You aren't using your DS.
