Know anything about AT&T Merlin systems?

I work for a nonprofit Walk-a-thon and we use donated space to set up our communication nerve center. There are five telephone lines coming into the space and the desire is to have four of them connected in such a way that when a given number is called, the call will bounce from busy phone to busy phone until there is a free phone. The goal is to give out one phone number to volunteers. The telephone company is contacted to put the four of the phone lines into a hunt group. For years, these 4 lines would be fed through a Merlin 410 system(http://en.wikipedia.org/wiki/AT&T_Merlin) and distributed to Merlin phones but this past year, one of the phones has been lost and only compatible phones work with the Merlin system. My question is: do we even need the merlin system or will we get the desired result with cheap phones and the hunt group?