Hi,
Does MAG4610 comes with a rack mount kit from the package?
Yes!
(http://www.juniper.net/techpubs/en_US/mag/topics/reference/general/mag-4610-rack-mount.html)
The datasheet mentions (Page 6):
http://www.juniper.net/us/en/local/pdf/datasheets/1000356-en.pdf
should be the same kit