Ask a manager has a recent post here about travel reimbursements. There's a lot of discussion in the comments about how the policies really differ significantly.
When I first started out and had zero money, my fieldwork happened to be local. So I wasn't really on the hook for travel expenses. By the time I started a lot of non-local travel, I had enough cash available to float the expense until the reimbursement check came in, so the issue of how to pay for my expenses was more about convenience.
I've had access to several different travel-payment arrangements:
1. Arrange for a travel advance. This was offered as a first option for folks who were entry-level or had just started the job. It was also the standard arrangement for reimbursement at my grad school, but I found it easier to pay whatever and get reimbursed later when I had the bill in hand. If someone is super new, the travel advance may go to the person in charge of the fieldwork to take care of the arrangements so that the company is reasonably sure the newbie isn't going to abscond with a big check.
2. Have admin/travel book everything. The charges go on some admin credit card or PO, it's one of the admin's primary tasks (so it's routine for them and there aren't any surprises) and all the of paperwork/approvals are taken care of by the financing folks.
3. Use your own credit card, which you've selected because of its favorable travel points (hotel or airline, usually - most folks I know stick with 1 main card to maximize status with one program). Get reimbursed when you submit your charges. As long as you're finding flights/hotels that are within the limits set out, nobody cares where you stay, so you pick the option that you get points on. Never pay for your own flights/hotels on your vacations again, but you are essentially giving your firm a series of advantageous short-term loans. You may have wild fluctuations in cash flow as reimbursements are paid, so this option requires enough credit/extra money to account for this.
4. Get a corporate card. Variations include:
a. All charges go to the company, don't worry about them. Expect a nastygram from A/P if you charge something unreasonably personal to it.
b. The company pays the credit card directly, but it's up to you to submit your bills/invoices/charge slips, and if you take too long, expect a nastygram from A/P.
c. The company pays the credit card directly, but only after you submit for reimbursement, and if you don't, your own credit gets dinged if the charge is late. How timely is your company's payment, anyway?
d. Here's a credit card. It has the corporate name on it, but otherwise, it's all yours. See 3 above, but with no travel point perks.
Right now, I have an ideal situation, which is that I have my choice of 2 or 3. If I did mostly fieldwork (not the case right now) and made a big stink, I probably could get 4a. If booking may be a pain or I may rack up a truly spectacular set of charges (back-to-back flights across the country with no notice, for instance), I'll go with 2. Otherwise, I'll keep up my super duper elite status on my travel-related credit card with 3.
I've submitted travel expenses for several different organizations, including for a sponsor of my masters' research which was a major resource company. I haven't had issues getting reimbursement, but I'm pretty careful to limit my reimbursed/company paid expenses to stuff that I actually need to travel/get fieldwork done.
The only time I ran into trouble was when I was required to use option 4c and I had to submit all my expenses in one report (i.e. after I got back and the hotel got around to billing the credit card) and I had to make advance reservations. Then, I was in danger of my credit card not being paid in time through no fault of my own, so I blew off the option 4c requirement and used my own damn credit card for the advance reservations.
I do think that environmental consulting firms are generally reasonable - most of the management has at least a dim memory of traveling for fieldwork, so things are usually arranged so that field staff aren't in danger of not having enough money or credit to do the work. But yes, it is pretty standard for employees in environmental consulting to pay for travel and get reimbursed later.