Edit: I went through the process again and now the turnaround at the local office is just one day. Also, only 4 photos are required, not 5.
I don't know whether this is true of all field offices, but do check before making assumptions.
Today I visited the Bureau of Immigration head office in Intramuros, and they informed me that the normal processing time is three days. (Exactly three days, to the minute. You cannot apply Monday afternoon and pick-up Thursday morning.) The exit clearance fees are included in the ACR I-Card (Alien Certificate of Registration), leaving "only" the P500 general transaction fee.
If you can make a couple round trips to Manila (or one round trip if your flight is late on a weekday), you can save a flight from having missed the provincial ECC deadline.
Since the requirements aren't listed online or even on the official application form, but only on a paper slip stapled onto it, this list might help if you're making a long trip:
- 5 pieces, 2-inch square glossy photos, passport-style (no eyeglasses or hat)
- You can buy a set on-site for P100.
- Photocopies of all passport pages containing Philippine visas and extensions up to the last entry
- Photocopy of passport info page
- Photocopy of ACR, front & back
- Photocopy of last visa extension receipt (!)
- Your passport, obviously
- Your hands. They will take a complete set of fingerprints, so there's no way to send an agent.