You will clear 45k in North Platte, no problem. The place is a meat market, so you will also move up pretty quick. Some guys hold road jobs after 12 - 18 months there, some guys hold RCO foreman jobs after only 6 months. This is unheard of in the industry, but then again, North Platte is an odd duck in the RR world and the normal rules dont apply there. A couple of things to consider when going to North Platte: number one, you will never, EVER leave that place once you are in. Transfers are unheard of because of the turnover there, so dont think for a minute that you can get some time in under your belt and then bolt back to Colorado. I made that mistake, and I had to get out of the business to get back home. The only exception to this is the rare guy who holds a job on the long pool from NOP to Cheyenne; I kenw a couple of guys who did this and they tried to live in Fort Collins or Greeley, but it was tough holding that job since it pays the best down there and a lot of old heads would bump on and off that pool dpending on whether or not it was hunting / football / fishing season...take your pick.
Antoher thing to consider is the managment in North Platte; I know a lot about this and if you want to look up some of my posts from the past you might get a good idea of what goes on there. Be prepared to face some very confrontational managers; there are some really good eggs amongst the mix, but you'll have to look for them. The TE&Y guys are on the whole good guys to work with; there are so many heads working there that the nasty of the nastiest oldheads are pretty spread out. On the flip side of that, since the demand for workers is so great, some not-so-great newguys get in the mix too. But by and large, the workforce there will help you out.
If you really want to make a career out of the railroad, North Platte is tough to beat in terms of advancement in seniority and if you ever have management ambitions, that is the place to go since turnover is high amonst the management ranks as well. They burn through MOPs and MYOs like nobody's business there, and there are a lot of guys from the ranks there who have made it up to the MTO, SMTO, and director level all right there in North Platte. If you prefer to stay in the ranks (I recommend that!), there are a lot of opportunites to hold engine school there and yardmaster spots are not all that uncommon. They even have terminal dispatchers there and those spots seemed to come up pretty quick as well.
The downside to the whole thing is North Platte will be your home for quite some time. Make sure your family is cool with this before you make the jump, because it will be like night and day from what they are used to in Colorado. I wasnt in north platte, but I was close enough, and I was spending every off day I could get my hands on back in Colorado acutally enjoying the fruits of civilization. Some people like the small town thing, and if you are good with that, go for it because it does have its merits. If not, dont bother, because it will get old real quick.