It will work fine - as long as the PICs are the only I2C devices on the bus. The I2C specification was written to deal with low-power devices that have no more than 2 mA drive. As a result, all the pull ups (in parallel) could be no smaller than 2.5K. Since a PIC pin will sink more than 20mA, you can use much smaller pull ups. If there are only two PICs on the bus, I regularly use a 1K pull up at each end, with 10 ohms in series (one at each end) to reduce ringing. Since your CAT-5 will be twisted pairs, use one wire of each pair as GND (and the other as SDA or SCL). You should have no trouble at distance of at least 50'. But if you do get errors, you can slow the I2C bus down to lower data rates.

Be aware, however that any other non-PIC devices on the bus will probably not be able to drive such small pullups properly.