(Sorry, misread the question...the below is for DHCP options to upstream clients, not for the EX Switch itself...let me check on that)
Yes, option 82 has been supported since JUNOS 9.3. Here is the output of the DHCP option configuration section in the CLI. You can configure options 1 through 255 and specific many possible catagories for each option.
CLI Output...
[edit system services dhcp]
admin@ex-switch# set option ?
Possible completions:
<option-identifier-code> DHCP option identifier code (1..255)
[edit system services dhcp]
admin@ex-switch# set option 82 ?
Possible completions:
<[Enter]> Execute this command
> array Array of values
byte Unsigned 8-bit value
byte-stream Stream of unsigned 8-bit values within quotes
flag Boolean flag value
integer Signed 32-bit numeric value
ip-address IP address value
short Signed 16-bit numeric value
string Character string value
unsigned-integer Unsigned 32-bit numeric value
unsigned-short Unsigned 16-bit numeric value
| Pipe through a command
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