As a Pakistani Shia, I will defend Pakistan from these baseless accusations from Iranian members here.
There is a porous Iranian/Pakistani border. I admit that Iran has better control of the border regions of Sistan-Balochistan than we do of our border region.
However, the founder of Jundullah (Iran) [which isn't the same as Jundullah (Pakistan)] was AbdulMalik Rigi. He was an Iranian, a Sunni from Sistan-Balochistan. He wasn't a Pakistani. There is good reason to believe that Jundullah fighters are actually (Balochi) Iranian citizens, that probably have sympathies amongst the local Baloch populations of both Iran and Pakistan. If the Islamic Republic of Iran did not discriminate so heavily against Sunni Balochi Iranians, things might be different.
Most members of Jundullah (Iran) will be disenfranchised Sunni Iranian Balochis, not Pakistanis. They will get some sympathy from Sunni Balochis in Balochistan, Pakistan.
But the impetus of the movement is from the disenfranchised Sunni Iranian Balochis, they are the heartbeat of Jundullah (Iran). There are probably sleeper cells in Zahedan too, that haven't been discovered.