If you want to select your own agent, here is how it has normally worked for me...Through various means (personal referral, this site, whatever) I establish a relationship with a potential client. We click. They explain they have a relo company that will be involved. Once they have the information and a case worker, they tell their case worker that they want to use me; and the potential client gives each of us the other's contact information. Once I am in contact with the relo company, it is up to me to negotiate my arrangement with the relo company. I will tell you that I have only had to pay them the 25% once... all other times I've successfully negotiated something else and sometimes don't pay them anything. it just depends. And, my broker gets nothing extra from me - but that varies by brokerage. In any case, the clients are MUCH happier with the result.
One last thought. Assume nothing. While most agents dread the words relo company; sometimes they are great. I had one client (this was a govt contractor) who was relocating and I sold their home. They paid ABOVE the going rate for commission, with no split required, which helped me to sell her house faster in a declining market.
In any case - find and agent you like. When you get the details on the relo company, put the agent and relo company in contact. Let them work it out. They will.
Normally the company that is moving you has a relocation dept. The relo department provides you with a "relocation package" to help you figure out your options.
Typically the relo dept. works with a relocation organization that provides assistance to both employers and their employees. Realtors and/or their brokers join one of these referral organizations and are referred buyers and sellers based on their skills, location, etc. They pay a fee, usually 25-35% of the commissions earned, to the relo organization (so the employees do not pay). The Realtors are screened and they usually offer an employee a couple of Realtors to interview, and they select the one that they believe will do the best job.
in the base of selling a property, an appraisal is done, then the normal agreement offers to purchase the property outright if it does not sell. Employers do not want to own employee properties, but sometimes that happens. In terms of the actual sale, the employee actually turns title over to the company, they in turn sell the property.
The amount of relocation assistance varies widely from company to company. Large companies may pay for moving, several weeks of hotel accommodations, trips back and forth to the new city, etc. Smaller companies may simply offer an allowance.
Because of the large shift in the housing market you should do your research up front and know what they will do for you. Most companies want motivated employees, not stressed out employees worried about their mortgage payment or their home that will not sell.
From the employee point of view, your move, that benefits the company, should not leave you any worse off after all is said and done.
Hope this helps.