It will not most certainly NOT count as an IPC.

121 currency is not 91 currency.

91 currency is based on you being the PIC, 121 SIC training does not count for that.

If your sim instructor is a CFI, and you can talk him into it, he can probably sign you off for a 91 IPC if you want one.

Just so there's no confusion...you may not need to be current for class, but you need to be current for an interview. Personally I would make sure I was instrument proficient before I attended my first 121 training event (whatever proficiency means to you).