Lucent 854 Phones & Telco Upgrade Prob!

My telco (Embarq) recently upgraded some equipment at the CO in my area. Since then, my Lucent 4-line phones won't "talk to each other". If someone else is on the line it rarely lights up to show that the line is busy and you can pick up in the middle of another person's conversation if you are not careful.

These phones apparently communicate with each other through line 1. There is no PBX. If you have people on say line 2 and 3, and pick up line 1, at that point lines 2 and 3 will light up- on your phone only.

I don't think it's coincidence that the day the phone company made this change, my phones stopped working properly... but I doubt they will help me with my problem.

Is there anything I can do to encourage these phones to communicate?