Private equity group TPG Capital and independent investment fund Global Infrastructure Partners (GIP) have made a non-binding proposal to buy all of Asciano through a scheme of arrangement.
Analysts say the indicative bid was opportunistic and that the predators could return with a higher offer.
The offer was for $4.40 cash per security or a scrip alternative of securities in "a bidding company".
Asciano on Monday said the bid undervalued its business and declined to allow the parties to conduct due diligence.
TPG and GIP are considering their response and are believed to be waiting to see Asciano's full year results announcement due on Wednesday.
GoldmanSachs JBWere analyst Jonathan Collett said Asciano's response was hardly surprising given that recent transactions in the ports and rail sector suggested it was worth substantially more under a takeover scenario.
Collett said that in his view Asciano had an underlying value of around $6.80 per security.
"Hence, on face value, this bid appears to be opportunistic," Collett said in a research note to clients.
"However, the parties to this consortium are genuine bidders with deep pockets, hence their pursuit of Asciano would appear unlikely to end here.
"Regardless of this, we expect the offer (albeit rejected) will have an ongoing positive impact, given it provides a floor under the share price and effectively puts Asciano in play to attract other potential bidders."
Asciano securities rose 21 cents, or 4.35 per cent, to $5.04 on Tuesday, after gaining just over 16 per cent on Monday.
Collett said the scenario surrounding the takeover bid could become complicated if Asciano announced a capital raising when it reported its annual results on Wednesday.
This might not only affect the consortium's proposal and other potential bidders. Some investors may shy away from contributing further capital before the potential for a higher bid from TPG and GIP or others is further explored.
JP Morgan analyst Matthew Crowe said the offer for Asciano was "far too low".
"We believe the offer would have to be at least $6.70 to have a reasonable chance of success," he said in a research note.
Crowe said Asciano was considering funding options that included equity raising or an asset sale, and the TPG-GIP offer reduced the likelihood of an equity raising.
"However, an asset sale of say 20 per cent of the ports at an attractive multiple would probably lead to a re-rating that could kill off the current offer," Crowe said.
UBS analyst Simon Mitchell said the outcome of any binding bid would depend on Asciano chief executive Mark Rowsthorn who holds a stake of around 10.5 per cent of the company.
Mitchell expects Asciano to report underlying earnings before interest, tax, depreciation and amortisation (EBITDA) of $662 million for the fiscal 2008 year.
This would be an improvement on its guidance for EBITDA of $650 million to $660 million and follows better than expected operating conditions.
"We expect management to outline its plans for expansion capex [capital expenditure] and funding sources at the result," Mitchell said in a client note.
"We expect capex of $1.5 billion over the next three years.
"Whilst we believe the business is in no immediate need of fresh capital, we would not rule out a partial sale of the business or equity issuance to reduce gearing."
Asciano's portfolio of assets includes the Pacific National rail haulage business and the Patrick ports and stevedoring business.
Asciano's growth initiatives include entry into the Queensland coal haulage market, a proposed investment in the Saudi Landbridge project and expansion of its Fisherman Islands container terminal in Brisbane.
