Ok, I will attempt to answer your questions, but I really have no idea what your coverage there is, so here goes:
Data transfer (web stuff) is adequate, but not even close to CDMA. Its digital technology is based on the PTT feature, and not real well suited to data transfer. It DOES work, but is slower, older technology in that respect.
As for how PTT works; there isnt a better PTT service out there. Verizon, AT&T, and others, have attempted their versions of PTT, but its simply VOIP, and is still an emerging technology, and has lots of problems. Sprint is marketing theirs as well, but I advise all my clients to stay on the iDEN network if its working for them. No need to buy into the hype (I am a business account manager, not a salesman, so I dont need to BS my customers). Our public safety people here use it ALL the time. the PTT doesnt have the same failure rate as calls, oddly enough. Also, the newer devices have what is referred to as DirectTalk-what this means is that the device is removed from the network, and can be used as a standard walkie talkie. You have to configure the handset to do this, and, if you are in DirectTalk mode, you will NOT receive any alerts from anyone on the network. Its good for several people who want to communicate in an area where there isnt any signal. Distance varies with terrain, much as with normal walkie talkies.
If your FD, PD, and military all use it, I would be suspect to them being on a closed network; here in the US, the FCC is pushing to move all public safety iDEN traffic to a private 700mHZ channel, and taking them off the public network. This is for two reasons; one, to avoid cross talk on the networks. Two, they will be able to maintain their OWN network, and it will be lisenced, much like their radio channels are. This provides security and a network that wont be overloaded when a natural disaster strikes.
My suggestion if you decide to go to an iDEN ready phone; go with a Powersource device (ic402, ic502, ic602, ic902, here in the US). I am not sure if you have CDMA or GSM coverage there, but the Powersource devices here work on BOTH the CDMA network (voice & data) and the iDEN network (Direct Connect). Its sort of the best of both worlds. The 402 & 502 dont have a camera though, and the 902 has extra bells & whistles. I had a 602 for 2 years, and would have kept it, but my nephew broke his phone, so I gave it to him. IMHO, I would go for the hybrid, if you can.
Coverage is going to depend entirely on whether you are covered in your area or not. If you go to Sprints main website, they have a coverage tool (not sure if it would work for you there or not though), and that will show you where coverage is for whatever network you are looking into.
If you have any other questions, let me know. I'll do my best to answer them for you.